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1. The Ordinary Conception of Perceptual Experience

In this section we spell out the ordinary conception of perceptual experience. There are two central aspects to this: Openness (§1.1) and Awareness (§1.2).

1.1 Openness

On our ordinary conception of perceptual experience, perceptual experience is a form of “openness to the world” McDowell (1994: 111). We understand this more precisely as follows:

Openness: Perceptual experience, in its character, involves the presentation (as) of ordinary mind-independent objects to a subject, and such objects are experienced as present or there such that the character of experience is immediately responsive to the character of its objects.

To clarify this, we can break it down into two components: Mind-Independence (§1.1.1), and Presence (§1.1.2).

1.1.1 Mind-Independence

The first component of Openness is,

Mind-Independence: perceptual experience involves the presentation (as) of ordinary mind-independent objects.

On ‘object’: we assume a broad understanding of ‘object’ to encompass perceptible entities in mind-independent reality including material objects, but also features and other entities (e.g., events, quantities of stuff). Mind-Independence is thus a claim otherwise expressed as follows: perceptual experience is a presentation of, or is as of, a public, mind-independent subject-matter. On ‘ordinary’: Mind-Independence concerns familiar perceptible things, things that we admit as part of common sense ontology.

As P.F. Strawson argued, reflection on ordinary perceptual experience supports a characterization of it in terms of Mind-Independence: “mature sensible experience (in general) presents itself as, in Kantian phrase, an immediate consciousness of the existence of things outside us” (1979: 97). Strawson begins his argument by asking how someone would typically respond to a request for a description of their current visual experience. He says that it is natural to give the following kind of answer: “I see the red light of the setting sun filtering through the black and thickly clustered branches of the elms; I see the dappled deer grazing in groups on the vivid green grass…” (1979: 97). There are two ideas implicit in this answer. One is that the description talks about objects and properties which are, on the face of it, things distinct from this particular experience. The other is that the description is “rich”, describing the nature of the experience in terms of concepts like deer and elms and the setting sun. The description of the experience is not merely in terms of simple shapes and colours; but in terms of the things we encounter in the “lived world” in all their complexity. As Heidegger puts it,

We never … originally and really perceive a throng of sensations, e.g., tones and noises, in the appearance of things…; rather, we hear the storm whistling in the chimney, we hear the three-engine aeroplane, we hear the Mercedes in immediate distinction from the Volkswagen. Much closer to us than any sensations are the things themselves. We hear the door slam in the house, and never hear acoustic sensations or mere sounds. (Heidegger (1977: 156); quoted in Smith (2002: 105))

It may be that descriptions of experience like this involve a commitment to the existence of things outside the experience; but surely it is possible to describe experience without this commitment? So let us suppose that we ask our imagined perceiver to repeat their description without committing themselves to the existence of things outside their experience, but without falsifying how their experience seems to them. Strawson claims that the best way for them to respond is to say “I had a visual experience such as it would have been natural to describe by saying that I saw…” and then to add the previous description of the trees and the deer etc. We give a description of our experience in terms of the ordinary objects of our world. And we do this even if we are trying not to commit ourselves to the existence of these objects.

Strawson’s claim that perceptual experience strikes us as if it satisfies what we’re calling Mind-Independence is not a philosophical theory, one that would (for example) refute scepticism, the view that we cannot know anything about the mind-independent world (see the entry on skepticism). Rather, it should be a starting point for philosophical reflection on experience (1979: 94). This is why this intuitive datum of consciousness is not supposed to rule out idealism, the view that the objects and properties we perceive are in fact mind-dependent (see the entry on idealism). The idealist need not disagree with Strawson that reflection on ordinary experience supports Mind-Independence. They will just hold that, for philosophical reasons, this is not how experience really is. Mind-Independence, they can say, is intuitively appealing but ultimately false as a characterization of experience and its objects.

1.1.2 Presence

The second component of Openness itself involves two components. First, the phenomenal character of an experience has something to do with its presented objects: experience is, in its character, a presentation of, or as of, ordinary objects; and second the character of perceptual experience involves the presentation of ordinary objects as present or there in that it is immediately responsive to the character of its objects.

Presence: the character of perceptual experience itself involves the presentation (as) of ordinary objects in such a way that it is immediately responsive to the character of its presented objects.

When we reflect upon how the phenomenal character of experience is, and try to “turn inwards” to describe the nature of the experience itself, the best way to do this is to describe the objects of experience and how they seem to us. It seems a simple matter to move to the further claim that the way these objects actually are is part of what determines the phenomenal character of an experience.

But this is to move too fast. For what can be said here about experience can also be said about belief: it is widely accepted that if I want to reflect upon the nature of my beliefs, the best way to do this is to describe the object or content of my belief: that is, what it is in the world that my belief is about. The things my beliefs are about can be as ‘objective’ as the things I perceive. So what is distinctive of the dependence of perceptual experience on its objects?

One answer is that when an object is perceptually experienced, it is experienced as “there”, “given” or “present to the mind” in a way in which it is not in belief, thought and many other mental states and events. Experience seems to involve a particular kind of “presence to the mind”. This “presence” goes beyond the mere fact that the objects of experience must exist in order for the experience to be veridical. For the objects of knowledge must exist too, but states of knowledge do not, as such, have presence in the same way as perceptual experiences—except, of course, in the case when one knows something is there by perceiving it. (Compare here the phenomenon Scott Sturgeon calls “scene immediacy” (2000: Chapter 1)).

So what is this perceptual presence? Compare perceptual experience with pure thought. Pure thought, like experience, goes straight out to the world itself. But a difference between them is that in the case of thought, how the object of thought is at the moment one is thinking of it does not in any way constrain one’s thinking of it; but in the case of perception it does. One’s perception of a snow covered churchyard is immediately responsive to how the churchyard is now, as one is perceiving it. But one’s (non-perceptual) thought need not be: in the middle of winter, one can imagine the churchyard as it is in spring, covered in autumn leaves, and one can think of it in all sorts of ways which are not the ways it presently is. This is not available in perception, because perception can only confront what is presently given: in this sense, it seems that you can only see or hear or touch what is there. It is because of this that perception is sometimes said to have an immediacy or vividness which thought lacks: this vividness derives from the fact that perceived objects and their properties are actually given to the perceiver when being perceived, and determine the nature of the character of the experience.

Openness is the combination of Mind-Independence, and Presence. It is most clearly understood when it applies to those perceptual experiences involved in genuine perception (e.g., when one sees a snow covered churchyard for what it is). But we understand Openness as applying more broadly to even perceptual experiences which don’t involve perceptual contact with the world. This is why we have formulated it in terms of the presentation ‘(as) of’ ordinary objects. For instance, take pure hallucinations of the sort we will consider in §2.2 below. Suppose one has an hallucination of a snow covered churchyard for what it is, even when there is no such churchyard there to be perceived. Here, Mind-Independence characterizes one’s experience. For one’s experience is still as of a public mind-independent scene: the apparent objects of such hallucinatory experiences are ordinary objects. And, in a sense, Presence holds. The hallucination is, in its character as of the snow covered churchyard, and the churchyard seems to be there, present to one, such that the character of the experience is constrained by that apparent scene.

1.1.3 Transparency

Some recent writers on perception have defended a thesis which has become known as the transparency of experience (see Harman (1990); Speaks (2009); Tye (1992, 1995, 2000); Thau (2002); and for critical discussions of this idea, Martin (2002), Smith (2008), Stoljar (2004) and Soteriou (2013)). Transparency is normally defined as the thesis that reflection on, or introspection of, what it is like to have an experience does not reveal that we are aware of experiences themselves, but only of their mind-independent objects. There are two claims here: (i) introspection reveals the mind-independent objects of experience, and (ii) introspection does not reveal non-presentational features of experience (that is, features of the character of experience not traceable merely to the appearance of some object or feature in the environment).

Transparency is similar to Openness. The latter claim does involve something like (i). But Transparency is not the same as Openness, for it is not obvious that (ii) is part of our intuitive conception of experience. We do not have to hold that the phenomenal character of experience is exhausted (or completely determined) by the nature of the objects and qualities which are presented in experience. This claim can be disputed. For example, a scene can look very different when one removes one’s glasses: one’s visual experience of the churchyard then becomes hazy and blurred. But it can be argued that this phenomenal difference in experience need not derive from any apparent or represented difference in the objects of experience. Rather, it seems to be a difference in the way in which those objects are experienced (although see Tye (2000) for a different understanding of this phenomenon). So there are reasons for thinking that (ii) is not part of the common sense conception of experience. (For further discussion on seeing blurrily see Smith (2008), Allen (2013), and French (2014). For a different challenge to (ii) see Richardson (2010) and Soteriou (2013: Chapter 5)).

1.2 Awareness

Openness can characterize perceptual experience which doesn’t involve genuine perceptual contact with the world. But it is part of our ordinary way of thinking about perceptual experience that we sometimes make perceptual contact with the world. Thus, we come to the second component of our ordinary conception of perceptual experience:

Awareness: perceptual experience sometimes gives us perceptual awareness of ordinary mind-independent objects.

For instance, in seeing a snow covered churchyard for what it is, one has a visual experience, and is visually aware of a snow covered churchyard. (Here we understand perception as a conscious state or event—as something which is or involves perceptual experience—which is a mode of awareness).

2. The Problem of Perception

The Problem of Perception is that if illusions and hallucinations are possible, then perception, as we ordinarily understand it, is impossible. The Problem is animated by two central arguments: the argument from illusion (§2.1) and the argument from hallucination (§2.2). (A similar problem has also been raised with reference to other perceptual phenomena such as perspectival variation or conflicting appearances, on which see Burnyeat (1979) and the entry on sense-data). For some classic readings on these arguments, see Moore (1905, 1910); Russell (1912); Price (1932); Broad (1965); and Ayer (1940), see Swartz (1965) for a good collection of readings. And for some fairly recent expositions see Snowdon (1992), Robinson (1994: Chapter 2); Smith (2002: Chapters 1 and 7), and Martin (2006).

In this section we present the arguments from illusion and hallucination both as challenging Awareness. That’s bad enough for our intuitive conception of perceptual experience, but it gets worse: for later we’ll see how the arguments can be supplemented so as they support the rejection of Openness too (§3.1).

2.1 The Argument from Illusion

According to Awareness, we are sometimes perceptually aware of ordinary mind-independent objects in perceptual experience. Such awareness can come from veridical experiences—cases in which one perceives an object for what it is. But it can also come from illusory experiences. For we think of an illusion as “any perceptual situation in which a physical object is actually perceived, but in which that object perceptually appears other than it really is” Smith (2002: 23). For example, a white wall seen in yellow light can look yellow to one. (In such cases it is not necessary that one is deceived into believing that things are other than they are). The argument from illusion, in a radical form, aims to show that we are never perceptually aware of ordinary objects. Many things have been called “the argument from illusion”. But the basic idea goes as follows:

  1. In an illusory experience, one is not aware of an ordinary object.
  2. The same account of experience must apply to both veridical and illusory experiences.
  3. Therefore, one is never perceptually aware of ordinary objects.

Four immediate comments on this are in order: First, as it stands this is an inadequate representation of the argument as it conceals the complex moves usually invoked by proponents and expositors, but we’ll try to improve on this soon (in particular, a fuller version includes a mini argument for (A)). Second, it is useful to represent the argument in this basic form to begin with as it enables us to highlight its two major movements; what Paul Snowdon calls the base case, and the spreading step (Snowdon 1992). In the base case a conclusion about just illusory experiences is sought: namely, (A). In the spreading step, (B), this result is generalized so as to get conclusion (C). Third, as we’re representing the argument here it is purely negative. But many philosophers have moved from this to the further conclusion that since we are always aware of something in perceptual experience, what we are aware of is a “non-ordinary” object (sometimes called a “sense-datum”). In §3.1, we will examine this further development. Finally, this argument is radical in that it concludes that we are never perceptually aware of ordinary objects. A less radical version concludes instead that we are never directly aware of ordinary objects, but for all that we may be indirectly aware of them. We’ll return briefly to this less radical version of the argument in §3.1 below. For now we’ll set aside complications to do with direct and indirect awareness.

Moving beyond the simple formulation, the argument from illusion is typically presented as involving these steps:

  1. In an illusory experience, it seems to one that something has a quality, F, which the ordinary object supposedly being perceived does not actually have.
  2. When it seems to one that something has a quality, F, then there is something of which one is aware which does have this quality.
  3. Since the ordinary object in question is, by hypothesis, not-F, then it follows that in cases of illusory experience, one is not aware of the object after all. (A).
  4. The same account of experience must apply to both veridical and illusory experiences. (B).
  5. Therefore, in cases of veridical experience, one is not aware of the object after all.
  6. If one is perceptually aware of an ordinary object at all, it is in either a veridical or illusory experience.
  7. Therefore, one is never perceptually aware of ordinary objects. (C).

This improves on the simple version of the argument in having both a fuller base case stage and a fuller spreading step. That is, the basis of premise (A) is made clear, and the spreading from (B) is expanded.

The most controversial premise in the argument is premise (ii). The other premises just reflect intuitive ways of thinking about perceptual experience, and so are unlikely to be targeted by one seeking to reject the argument from illusion. This is clear enough with premises (i) and (vi), but what about premise (iv)? What this means is that the account of the nature and objects of illusory and veridical experiences must be the same. Though it may be disputed, this premise seems plausible. For veridical and illusory experiences both seem to be cases where one is aware of an ordinary object. The only difference is that in the illusory case, but not in the veridical case, the object one is aware of appears some way other than it in fact is.

Premise (ii) is what Howard Robinson has usefully labelled the “Phenomenal Principle”:

If there sensibly appears to a subject to be something which possesses a particular sensible quality then there is something of which the subject is aware which does possess that sensible quality (1994: 32).

C.D. Broad motivates this principle on explanatory grounds. In cases of perceptual experience things appear some ways rather than others to us. We need to explain this. Why does the penny one sees look elliptical to one as opposed to some other shape? One answer is that there is something of which one is aware which is in fact elliptical. Thus as Broad says “If, in fact, nothing elliptical is before my mind, it is very hard to understand why the penny should seem elliptical rather than of any other shape.” (1923: 240). Other philosophers have simply taken the principle to be obvious. H.H. Price, for example, says that “When I say ‘this table appears brown to me’ it is quite plain that I am acquainted with an actual instance of brownness” (Price 1932: 63).

So much for the argument’s main premises. How is it supposed to work? Here we find the suggestion that it hinges on an application of Leibniz’s Law of the Indiscernibility of Identicals (Robinson (1994: 32); Smith (2002: 25)). The point is that (i) and (ii) tell us that in an illusory experience one is aware of an F thing, but the ordinary object supposedly being perceived is not F, thus the F thing one is aware of and the ordinary object are not identical, by Leibniz’s Law. On these grounds, the conclusion of the base case stage is supposed to follow. And then the ultimate conclusion of the argument can be derived from its further premises.

But as French and Walters (forthcoming) argue, this is invalid. (i), (ii) and Leibniz’s Law entail that in an illusory experience one is directly aware of an F thing which is non-identical to the ordinary object supposedly being perceived. But this doesn’t entail that in the illusion one is not directly aware of the ordinary object. One might be aware of the ordinary object as well as the F thing one is aware of. We should be careful to distinguish not being (directly) aware of the wall from being (directly) aware of something which is not the wall. The argument is invalid in conflating these two ideas.

One option for fixing the argument is to introduce what French and Walters call the Exclusion Assumption (cf., Snowdon (1992: 74)):

If in an illusion of an ordinary object as F one is aware of an F thing non-identical to the ordinary object, one is not also aware of the ordinary object.

This assumption bridges the gap between the conclusion actually achieved:

(iii*) in an illusory experience one is aware of an F thing non-identical to the ordinary object

and the desired conclusion (iii). But whether this assumption is defensible remains to be seen. In the remainder we leave this and the issue of validity aside and consider responses from different theories of experience.

2.2 The Argument from Hallucination

A hallucination is an experience which seems exactly like a veridical perception of an ordinary object but where there is no such object there to be perceived. Like illusions, hallucinations in this sense do not necessarily involve deception. And nor need they be like the real hallucinations suffered by the mentally ill, drug-users or alcoholics. They are rather supposed to be merely possible events: experiences which are indistinguishable for the subject from a genuine perception of an object. For example, suppose one is now having a veridical perception of a snow covered churchyard. The assumption that hallucinations are possible means that one could have an experience which is subjectively indistinguishable—that is, indistinguishable by the subject, “from the inside”—from a veridical perception of a snow covered churchyard, but where there is in fact no churchyard there to be perceived. (For more on hallucination, see the essays collected in Macpherson and Platchias (2013)).

A radical form of the argument again challenges Awareness:

  1. An hallucinatory experience as of an ordinary object as F is not a case of awareness of an ordinary object.
  2. Veridical experiences of ordinary objects as F and their hallucinatory counterparts are to be given the same account.
  3. Therefore, one is not perceptually aware of ordinary objects in veridical experience.

What this argument shows, if it is successful, is that one is not perceptually aware of ordinary objects in veridical experiences. The conclusion here is not as general as the conclusion of the argument from illusion, but the more general conclusion is surely not far off: for it would be difficult to maintain that though one is not perceptually aware of ordinary objects in veridical experiences, there are other cases of experience where one is perceptually aware of ordinary objects. So this argument supports if not entails the rejection of our ordinary conception of perceptual experience. Its aim is to show that an aspect of our ordinary conception of perception is deeply problematic, if not incoherent: perceptual experience cannot be what we intuitively think it is. (It is essentially this problem which Valberg (1992) calls “the puzzle of experience”.) But as with the argument from illusion, the argument can be developed, in supplemented form, to defend the conclusion that we only ever perceptually aware of “non-ordinary” objects (see §3.1).

Once again we can view the argument as having a base case (A) and a spreading step (B) (Snowdon 2005). Unlike with the argument from illusion, the base case here is less controversial: it doesn’t rely on the Phenomenal Principle. We thus don’t need a more complicated argument to support it. (A) simply falls out of what hallucinations are supposed to be, and two principles: first, that awareness of an object is a relation to an object, and second, that relations entail the existence of their relata. For given our principles, if an hallucination as of an ordinary object is to be a mode of awareness of an ordinary object then there must be an ordinary object there for one to perceive. But no such objects are there in hallucinations, therefore, hallucinations are not cases of awareness of ordinary objects.

Where the argument from hallucination is controversial is in the spreading step. The spreading step here gets construed in terms of the idea that veridical experiences and hallucinations are essentially the same; mental events of the same fundamental kind (Martin (2006)). (This doesn’t mean that we lose a distinction between veridical experiences and hallucinations. It just means that the difference between veridical experience and hallucination is not to be found in their intrinsic natures). This claim seems plausible, as from a subject’s perspective an hallucination cannot be told apart from a veridical experience. Thus some will accept (B) and thus deny that we are ever perceptually aware of ordinary objects (see sense-datum theories §3.1), and others will accept (B) but argue that we can still have perceptual awareness of ordinary objects (see intentionalist theories §3.3). But as we’ll see, others will want to secure perceptual awareness of ordinary objects by rejecting (B) and holding that hallucinations and veridical experiences are fundamentally different (see naive realist theories and disjunctivism §3.4).

Though it is not plausible to deny the possibility of illusory experiences (though we may argue about how best to construe them; Anthony (2011) and Kalderon (2011)), the claim that subjectively indistinguishable hallucinations are possible is a little more controversial. How do we really know that experiences like this are possible? (Austin (1962), for instance, expresses scepticism). One way to answer this—though certainly not the only way—is to appeal to a broad and uncontroversial empirical fact about experience: that it is the upshot or outcome of a causal process linking the organs of perception with the environment, that our experiences are the effects of things going on inside and outside our bodies. If this is so, then we can understand why hallucinations are a possibility. For any causal chain reaching from a cause C1 to effect E, there are intermediate causes C2, C3 etc., such that E could have been brought about even if C1 had not been there but one of the later causes (see the entry on the metaphysics of causation). If this is true of causal processes in general, and perceptual experience is the product of a causal process, then we can see how it is possible that I could have an experience of the churchyard which was brought about by causes “downstream” of the actual cause (the churchyard). (This plays into the causal argument discussed in §3.4).

3. Theories of Experience

In this section we will consider the leading theories of experience of the last hundred years. These theories are understood here as responses to the Problem of Perception. (There are a number of theories of perception which are not discussed in this entry, either because they are not responses to this specific problem (like the causal theory of Grice (1961) and Lewis (1988), and Burge (2010)) or because they require an entire entry of their own (like the phenomenology of Husserl (1900–1) and Merleau-Ponty (1945); see the entry on phenomenology)).

As we understand theories of experience, they operate on two levels. On one level they tell us about the nature or structure of experience, on another level they tell us how what is said at the first level bears on grounding or explaining the phenomenal character of experience. Crudely, and with details and qualifications to explored below:

  • The Sense-Datum Theory: Level 1: experience is fundamentally a relation to a non-ordinary object; a sense-datum. Level 2: the character of experience is explained by the real presence of sense-data and their qualities in experience (§3.1).

  • The Adverbial Theory: Level 1: experience is non-relational and fundamentally a state of mind adverbially modified in a certain way (e.g., visually sensing brownly). Level 2: the character of experience is explained by the intrinsic qualities of experience which constitute the ways in which it is modified (§3.2).

  • The Intentionalist Theory: Level 1: experience is non-relational and fundamentally a matter of representing ordinary objects in certain ways. Level 2: the character of experience is explain by its representational nature (§3.3).

  • The Naive Realist Theory: Level 1: experience is fundamentally a relation to ordinary aspects of mind-independent reality. Level 2: the character of experience is explained by the real presence of ordinary aspects of mind-independent reality in experience (§3.4).

(In this exposition we do not consider much the possibility of mixed or hybrid views).

Here is what we find: The sense-datum theorist rejects our ordinary conception of perceptual experience. The adverbial theorist tries to improve upon the sense-datum theory, and holds on to Awareness. But it is unclear how they can secure Openness. Intentionalists and naive realists hold to both Openness and Awareness, but they do so in different ways, and with different responses to the Problem of Perception. (The way these positions emerge in response to the Problem of Perception is mapped most clearly in Martin (1995, 1998, 2000)).

3.1 The Sense-Datum Theory

3.1.1 The Sense-Datum Theory and The Problem of Perception

On the sense-datum theory, a perceptual experience in which something appears F to one consists in a relation of perceptual awareness to something which is actually F (Level 1). So whenever a subject has a sensory experience, there is something of which they are perceptually aware. This relational conception of experience is sometimes called an “act-object” conception, since it posits a distinction between the mental act of sensing, and the object which is sensed.

A sense-datum theorist calls the object of an experience a sense-datum. We can thus re-formulate the Phenomenal Principle espoused by the sense-datum theorists in these terms:

If there sensibly appears to a subject to be something which possesses a particular sensible quality F then there is something—a sense-datum—of which the subject is directly aware which does possess that sensible quality.

For the sense-datum theorist, the character of an experience is somehow explained (at least in part) by the sensible qualities of the sense-datum one is aware of. (Level 2). Consider an experience which one would describe in terms of seeing a snow covered churchyard for what it is. We can isolate certain aspects of the phenomenal character of such an experience, such as the appearance of whiteness to one. We want a theory of experience to explain such aspects. The sense-datum theorist will claim that things appearing white to you consists in your perceptual awareness of a white sense-datum. The character of your experience is explained by an actual instance of whiteness manifesting itself in experience.

Now ultimately the sense-datum theory opposes our ordinary conception of experience, but it doesn’t as we have it so far. For at the moment we have no opposition between sense-data and ordinary objects. Suppose that one has an experience of a churchyard as described above, and so one is perceptually aware of a white sense-datum. Now suppose one’s experience is veridical. Well, for all we’ve said, the sense-datum one is aware of could be an ordinary bit of mind-independent reality: some white snow. This is not ruled out, for a sense-datum is just whatever it is that one is aware of in a perceptual experience which instantiates the sensible qualities which characterize the phenomenology of one’s experience. All we know about sense-data is that they must satisfy two conditions:

  1. sense-data are objects of direct awareness; and
  2. sense-data bear sensible qualities.
But these conditions don’t mark out an interesting ontological kind (Austin (1962)). They are consistent with sense-data (sometimes) being ordinary objects and aspects of mind-independent reality. Call the sense-datum theory we have outlined so far a minimal sense-datum theory.

But paradigm sense-datum theories are, in contrast, non-minimal. And such non-minimal sense-datum theorists do reject our ordinary conception of perceptual experience. We can make sense of this if we move to a less minimal conception of sense-data themselves, on which they are not ordinary aspects of mind-independent reality. One option here is to articulate a theory of sense-experience and sense-data independently of the problem of perception (Jackson (1977) and Lowe (1992)). But by far the most popular approach for sense-datum theorists has been to move to a more committed conception of sense-data on the basis of arguments like the argument from illusion and the argument from hallucination. How does this work?

Take first the argument from illusion. Suppose one sees a white wall as yellow. The sense-datum theorist accepts the base case of the argument, along with Leibniz’s Law, and so holds that in the illusion one is aware of a yellow sense-datum which is not the wall. And suppose the illusion occurs in a world devoid of ordinary objects which are in fact yellow. Thus the sense-datum is a non-ordinary object. Suppose we accept further that in illusions we are directly aware of such non-ordinary sense-data instead of and not as well as the relevant ordinary objects. So illusions are cases where one is directly aware of just a non-ordinary sense-datum. With this the sense-datum theorist accepts the spreading step and concludes that no perceptual experience is a case of awareness of an ordinary object, and that illusory and veridical experiences are cases of awareness of non-ordinary sense-data.

We can run a similar line of thought with the argument from hallucination. Suppose one has an hallucinatory experience as of a churchyard covered in white snow. But there is no such churchyard there to be perceived. The sense-datum theorist conceives of this experience as a case of perceptual awareness of a white sense-datum. Suppose the hallucination occurs in a world devoid of ordinary white things, so the sense-datum one is aware of is a non-ordinary sense-datum. The sense-datum theorist then endorses the spreading step stage of argument to get the conclusion that even in veridical experiences one is aware of just non-ordinary sense-data.

Initially, the arguments from illusion and hallucination were presented as aiming for a negative claim. But what we’ve seen here is that the minimal sense-datum theorist can supplement the base case with further considerations so as to get not just the negative conclusion but a positive conclusion, which is itself generalised in the spreading step stage. That is, in combination:

  1. Base Case: (a) illusions and hallucinations are not cases of awareness of ordinary objects; but instead (b) are cases of awareness of non-ordinary sense-data.
  2. Spreading Step: veridical experiences, illusions and hallucinations are to be given the same account.
  3. Conclusions: (c) no perceptual experience is a case of awareness of an ordinary object; but instead (d) all perceptual experiences are cases of awareness of non-ordinary sense-data.

The arguments, understood as such, are not arguments for the minimal sense-datum theory—the arguments presuppose such a theory. Rather, they serve as arguments for the transition from the minimal form of the sense-datum theory to the non-minimal form which invokes non-ordinary sense-data.

From now on when we speak of “sense-data” we will mean non-ordinary sense-data. Sense-datum theorists will divide over exactly how to understand sense-data insofar as they are non-ordinary. The early sense-datum theorists (like Moore (1914)) considered sense-data to be mind-independent, but non-physical objects. Later theories treat sense-data as mind-dependent entities (Robinson (1994)), and this is how the theory is normally understood in the second half of the twentieth century. What these different workings out of the theory have in common, though, is that they stand opposed to our ordinary conception of perceptual experience in both its aspects. On the non-minimal sense-datum theory, perceptual experiences are presentations not of ordinary objects, but of sense-data, and the character of experience, though dependent on its objects, is thus dependent upon non-ordinary objects. Thus Openness is false. The sense-datum theorist need not deny that we are presented with objects as if they are ordinary objects. But they will insist that this is an error. (So sense-datum theories are not simply refuted (as Harman 1990 seems to argue) by pointing to the phenomenological fact that the objects of experience seem to be the ordinary things around us). And in perceptual experience we are not aware of ordinary objects but non-ordinary sense-data. Thus Awareness is false.

3.1.2 Indirect Realism and Phenomenalism

Must a non-minimal sense-datum theorist deny Awareness? It seems not. Some sense-datum theorists introduce a distinction between direct and indirect awareness. With this, they don’t deny that we are ever perceptually aware of ordinary objects, only that we are ever directly perceptually aware of ordinary objects. The sense-datum theorist can say that we are indirectly aware of ordinary objects: that is, aware of them by (in virtue of) being aware of sense-data. A sense-datum theorist who says this is known as an indirect realist or representative realist, or as someone who holds a representative theory of perception (see Jackson (1977), Lowe (1992); see also the entry on epistemological problems of perception). A theorist who denies that we are aware of mind-independent objects at all, directly or indirectly, but only of sense-data construed as mental entities, is known as a phenomenalist or an idealist about perception (see Foster (2000) for a recent defence, see Crane and Farkas (2004: Section 2) for an introduction to the subject; and the entry on idealism).

On the face of it the indirect realist form of the sense-datum theory salvages something of our ordinary conception of perceptual experience, but securing Awareness. But this shouldn’t be at all satisfying to one who wants to defend our intuitive conception of perceptual experience, for two reasons. First, Openness is still being denied. Second, once we are given the distinction between direct and indirect perception, a defender of our ordinary conception of perceptual experience is likely to uphold Awareness in a more specific form, that is, as the idea that perceptual experience sometimes gives us direct awareness of ordinary objects. That is, the main theories of experience which uphold our ordinary conception of perceptual experience—intentionalism and naive realism—are both usually regarded as versions of direct realism.

3.1.3 Objections to the Sense-Datum Theory

The sense-datum theory was widely rejected in the second half of the 20th century, though it still had its occasional champions in this period (e.g., Jackson (1977), O’Shaughnessy (1980, 2000, 2003), Lowe (1992), Robinson (1994), Foster (2000)). A number of objections have been made to the theory. Some of these objections are objections specifically to the indirect realist version of the sense-datum theory: for example, the claim that the theory gives rise to an unacceptable “veil of perception” between the mind and the world. The idea is that the sense-data “interpose” themselves between perceivers and the mind-independent objects which we normally take ourselves to be perceiving, and therefore leaves our perceptual, cognitive and epistemic access to the world deeply problematic if not impossible. In response to this, the indirect realist can say that sense-data are the medium by which we perceive the mind-independent world, and no more create a “veil of perception” than the fact that we use words to talk about things creates a “veil of words” between us and the things we talk about. (For recent discussion see Silins (2011)).

A common objection in contemporary philosophy is to attack the Phenomenal Principle (see Barnes (1944–5); Anscombe (1965)). The objection is that the Phenomenal Principle is fallacious. It is not built into the meaning of “something appears F to one” that “one is aware of an F thing”. Defenders of the sense-datum theory can respond that the Phenomenal Principle is not supposed to be a purely logical inference; it is not supposed to be true simply because of the logical form or semantic structure of “appears” and similar locutions. Rather, it is true because of specific phenomenological facts about perceptual experience. But this just means that theorists who reject the Phenomenal Principle are not disagreeing about whether the Phenomenal Principle involves a fallacy or about some semantic issue, but rather about the nature of experience itself.

Another influential objection to sense-data comes from the prevailing naturalism of contemporary philosophy. Naturalism (or physicalism) says that the world is entirely physical in its nature: everything there is supervenes on the physical, and is governed by physical law. Many sense-datum theorists are committed to the claim that non-ordinary sense-data are mind-dependent: objects whose existence depends on the existence of states of mind. Is this consistent with naturalism? If so, the challenge is to explain how an object can be brought into existence by the existence of an experience, and how this is supposed to be governed by physical law.

Many contemporary sense-datum theorists, however, will not be moved by this challenge, since they are happy to accept the rejection of naturalism as a consequence of their sense-data theory (see Robinson 1994, Foster 2000). On the other hand, one might think that there is no conflict here with naturalism, as long as experiences themselves are part of the natural order. But if sense-data are non-ordinary in being mind-independent but non-physical, then it is much less clear how naturalism can be maintained (cf., what Martin (2004, 2006) calls “experiential naturalism” which serves as a constraint on theories of experience and rules out some but not all forms of the sense-datum theory).

3.2 The Adverbial Theory

3.2.1 The Adverbial Theory and the Problem of Perception

Some philosophers agree with the Phenomenal Principle that whenever a sensory quality appears to be instantiated then it is instantiated, but deny that this entails the existence of sense-data. Rather, they hold that we should think of these qualities as modifications of the experience itself (Level 1). Hence when someone has an experience of something brown, something like brownness is instantiated, but in the experience itself, not an object. This is not to say that the experience is brown, but rather that the experience is modified in a certain way, the way we can call “perceiving brownly”. The canonical descriptions of perceptual experiences, then, employ adverbial modifications of the perceptual verbs: instead of describing an experience as someone’s “visually sensing a brown square”, the theory says that they are “visually sensing brownly and squarely”. This is why this theory is called the “adverbial theory”; but it is important to emphasise that it is more a theory about the phenomenal character of experience itself (Level 2) than it is a semantic analysis of sentences describing experience.

Part of the point of the adverbial theory, as defended by Ducasse (1942) and Chisholm (1957) was to do justice to the phenomenology of experience whilst avoiding the dubious metaphysical commitments the sense-datum theorists take on in responding to the Problem of Perception. The only entities which the adverbialist needs to acknowledge are subjects of experience, experiences themselves, and ways these experiences are modified. This makes the theory appear less controversial than the sense-datum theory.

3.2.2 The Adverbial Theory and Qualia

When used in a broad way, “qualia” picks out whatever qualities a state of mind has which constitute the state of mind’s having the phenomenal character it has. In this broad sense, any conscious state of mind has qualia. (This is the way the term is used in, e.g., Chalmers (1996)) Used in a narrow way, however, qualia are non-intentional, intrinsic properties of experience: properties which have no intentional or representational aspects whatsoever. To use Gilbert Harman’s apt metaphor, qualia in this sense are “mental paint” properties (1990). Harman rejects mental paint, the idea of experience as involving mental paint is taken up and defended by Block (2004)).

It is relatively uncontroversial to say that there are qualia in the broad sense. It can be misleading, however, to use the term in this way, since it can give rise to the illusion that the existence of qualia is a substantial philosophical thesis when in fact it is something which will be accepted by anyone who believes in phenomenal character. (Hence Dennett’s (1991) denial of qualia can seem bewildering if “qualia” is taken in the broad sense). It is controversial to say that there are qualia in the narrow sense, though, and those who have asserted their existence have therefore provided arguments and thought-experiments to defend this assertion (see Block (1997), Peacocke (1983 Chapter 1), Shoemaker (1990)). In what follows, “qualia” will be used exclusively in the narrow sense.

The adverbial theory is committed to the view that experiencing something red, for example, involves one’s experience being modified in a certain way: experiencing redly. The most natural way to understand this is that the experience is an event, and the modification of it is a property of that event. Since this property is both intrinsic (as opposed to relational or representational) and phenomenal (that is, consciously available) then this way of understanding the adverbial theory is committed to the existence of qualia.

3.2.3 Objections to the Adverbial Theory

An important objection to the adverbial theory has been proposed by Frank Jackson (1975). Consider someone who senses a brown square and a green triangle simultaneously. The adverbial theory will characterise this state of mind as “sensing brownly and squarely and greenly and triangularly”. But how can it distinguish the state of mind it is describing in this way from that of sensing a brown triangle and a green square? The characterisation fits that state of mind equally well. Obviously, what is wanted is a description according to which the brownness “goes with” the squareness, and the greenness “goes with” the triangularity. But how is the theory to do this without introducing objects of experience—the things which are brown and green respectively—or a visual field with a spatial structure? The challenge is whether the adverbial theory can properly account for the spatial structure and complexity in what is given in visual experience. (See Tye (1984) for an attempt to respond to this challenge.)

A related objection concerns the relationship between the adverbial theory and our ordinary conception of experience. The adverbial theorist might admit that, in a sense, we are aware of ordinary objects. When one “senses redly“ if this state of mind is appropriately caused by a red thing (e.g., a tomato), perhaps this is what being aware of such an object amounts to. And it is not as if such awareness is indirect or mediated by sense-data. However, it is not at all clear that the adverbialist is in a position to secure Openness. For the adverbialist rejects not just the idea that experience has a genuine act-object structure, but the idea that the character of experience is even a presentation as of ordinary things and qualities. Qualities get into the picture, and are constitutive of phenomenal character, but not by being presented from outside of experience as qualities of things, as Openness would have it. How, then, can the adverbialist account even for the appearance of an act-object structure within experience, for Openness? It is unclear how the adverbialist is to answer this question (see Martin (1998); Crane (2000)). And so it is unclear how much of an improvement the adverbial approach, and the qualia theory, is over the sense-datum theory.

3.3 The Intentionalist Theory

3.3.1 The Intentionalist Theory and the Problem of Perception

At Level 1, the intentional theory of experience treats perceptual experience as a form of intentionality conceived of as a form of mental representation (hence it is also sometimes called the representationalist theory of experience). “Intentionality” is a term with its origins in scholastic philosophy (see Crane 1998b), but its current use derives from Brentano (1874), who introduced the term “intentional inexistence” for the “mind’s direction upon its objects”. Intentional inexistence, or intentionality, is sometimes explained as the “aboutness” of mental states (see the entries on Franz Brentano, representational theories of consciousness and intentionality). An intentional mental state is normally understood, therefore, as one which is about, or represents, something in the world.

At Level 2, this is put to work in explaining phenomenal character. Take an experience as of a churchyard covered in white snow. Why is this a case of things appearing white to one? Here the intentionalist appeals to the experience’s representation of whiteness in the environment. It is not generally true that when a representation represents something as being F, there has to actually be something which is F. Thus for the intentionalist, experience is representational in a way that contrasts with it being relational. Experience does not genuinely have an act-object structure. This is in keeping with a standard tradition in the theory of intentionality which treats it as non-relational (the tradition derives from Husserl 1900/1901; for discussion see Zahavi 2003: 13–27). So intentionalism contrasts with the sense-datum theory: since it is not of the essence of experience or its character that it is relational, it is not of its essence that it is a relation to a non-ordinary sense-datum.

The intentionalist can thus reject the argument from illusion in the form presented in §2.1 and the supplemented form presented in §3.1.1. This is because these arguments hinge on the minimal sense-datum theory, or the Phenomenal Principle which the intentional theory is an alternative to. An illusory experience in which a white wall appears yellow to one is thus not conceived of as a case in which one is aware of a yellow sense-datum. It is instead conceived of as a case in which a white wall is represented as being yellow. As we’ll see, the intentionalist can even maintain the intuitive idea that in such illusions one is aware of the ordinary objects one seems to be aware of—but that’s something we’ll come back to shortly.

What about hallucinations? Again the intentionalist can reject the supplemented form of the argument from hallucination from §3.1.1 because this version of the argument relies on the Phenomenal Principle. But what about the original form of the argument from hallucination? This argument does not rely on the Phenomenal Principle, yet its conclusion is that not even veridical experiences give us direct awareness of ordinary mind-independent objects. So how is the intentionalist to deal with this argument? The intentionalist accepts (A) but also (B) in a specific form. That is, they accept (B) where that is understood in terms of what Martin (2004, 2006) has called the Common Kind Assumption, that is:

(CKA) Whatever fundamental kind of mental event occurs when one veridically perceives, the very same kind of event could occur were one hallucinating.

Take a veridical perception of a white snow covered churchyard for what it is. The experience involved in this perception, the intentionalist thinks, is fundamentally a matter of experientially representing the presence of a white snow covered churchyard. And this fundamental kind of mental event is exactly what is present in the subjectively indistinguishable hallucinatory case, for such hallucinatory experiences have the same representational nature as their veridical counterparts.

But then doesn’t this mean that the intentionalist is saddled with the conclusion of the argument from hallucination (C)? If so, the rejection of Awareness and our ordinary conception of perceptual experience is not far off. Since if we are not perceptually aware of ordinary objects in veridical experiences, it is unclear how any form of perceptual awareness of ordinary objects can be secured.

However, the intentionalist can distinguish between two readings of the conclusion. On the first reading, we have

(C*) veridical experiences are not fundamentally cases of awareness of ordinary objects.

This is entailed by the argument as we have construed it. But what is not entailed is

(C**) veridical experiences don’t give us perceptual awareness of ordinary objects.

As long as (C**) doesn’t follow, the intentionalist can suggest, Awareness is secure. The intentionalist admits that not even veridical experiences are fundamentally cases of perceptual awareness of ordinary objects. Such experiences are fundamentally representational in a way that contrasts with them being relational. But that simply doesn’t mean that we can’t come to be perceptually aware, even directly perceptually aware, of an ordinary object by having a veridical experience. Veridical experiences may be the occasions for such awareness even if they are not themselves constituted by instances of such awareness. They can be occasions for such awareness precisely because they represent ordinary objects. In their very character they are about, directed on, the mind-independent world (in contrast to both sense-datum theories, and adverbialist theories). We come to have (direct) perceptual awareness by having such experiences when the world also plays its part: when things in the world are as they are represented to be in the experience, and when the world is hooked up to the experience in an appropriate way. This also helps us to see how even illusions can give us (direct) awareness of ordinary objects. In these cases, experience represents an ordinary object which is there to be perceived, and it is appropriately related to one’s experience, yet there is some misrepresentation of the object.

Thus the intentionalist can respond to Problem of Perception: it has solutions to both arguments which animate the Problem. And the intentionalist response secures both aspects of our ordinary conception of perceptual experience. The intentionalist explains how experience satisfies Openness in terms of it having a certain sort of representational nature. That is, a perceptual experience involves, in its very character, the presentation of ordinary mind-independent objects to a subject precisely because it is a matter of perceptual representation of ordinary aspects of the environment. And such aspects are represented as there, present. The character of experience is immediately responsive to the character of its objects because it is constituted, at least in part, by the way those objects are represented, at the time they are experienced.

3.3.2 Sources of the Intentionalist Theory

Some of the most influential intentional theories are Anscombe (1965), Armstrong (1968), Pitcher (1970), Peacocke (1983), Harman (1990), Tye (1992, 1995), Dretske (1995), Lycan (1996); for more recent accounts, see Byrne (2001), Siegel (2010), Pautz (2010) and the entry on the contents of perception.

Within analytic philosophy, the intentionalist theory of perception is a generalisation of an idea presented by G.E.M. Anscombe (1965), and the “belief theories” of D.M. Armstrong (1968) and George Pitcher (1970). (Within the phenomenological tradition intentionality and perception had always been discussed together: see the entry on phenomenology.) Anscombe had drawn attention to the fact that perceptual verbs satisfy the tests for non-extensionality or intensionality (see the entry on intensional transitive verbs). For example, just as ‘Vladimir is thinking about Pegasus’ is an intensional context, so ‘Vladimir has an experience as of a pink elephant in the room’ is an intensional context. In neither case can we infer that there exists something Vladimir is thinking about, or that there is exists something he is experiencing. This is the typical manifestation of intensionality. Anscombe regarded the error of sense-data and naive realist theories of perception as the failure to recognise this intensionality.

Armstrong and Pitcher argued that perception is a form of belief. (More precisely, they argued that it is the acquisition of a belief, since an acquisition is a conscious event, as perceiving is; rather than a state or condition, as belief is.) Belief is an intentional state in the sense that it represents the world to be a certain way, and the way it represents the world to be is said to be its intentional content. Perception, it was argued, is similarly a representation of the world, and the way it represents the world to be is likewise its intentional content. The fact that someone can have a perceptual experience that a is F without there being any thing which is F was taken as a reason for saying that perception is just a form of belief-acquisition.

The belief theory of perception (and related theories, like the judgement theory of Craig (1976)) is a specific version of the intentional theory. But it is not the most widely accepted version (though see Glüer (2009) for a recent defence). Everyone will agree that perception does give rise to beliefs about the environment. But this does not mean that perception is simply the acquisition of belief. One obvious reason why it isn’t, discussed by Armstrong, is that one can have a perceptual illusion that things are a certain way even when one knows they are not (this phenomenon is sometimes called “the persistence of illusion”). The famous Müller-Lyer illusion presents two lines of equal length as if they were unequal. One can experience this even if one knows (and therefore believes) that the lines are the same length. If perception were simply the acquisition of belief, then this would be a case of explicitly contradictory beliefs: one believes that the lines are the same length and that they are different lengths. But this is surely not the right way to describe this situation. (Armstrong recognised this, and re-described perception as a “potential belief”; this marks a significant retreat from the original claim). The intentionalist theory is, however, not committed to the view that perceptual experience is belief; experience can be a sui generis kind of intentional state or event (see Martin 1992–3).

3.3.3 The Intentional Content of Perceptual Experience

Intentionalists hold that what is in common between perceptions and indistinguishable hallucinations is their intentional content: roughly speaking, how the world is represented as being by the experiences. Many intentionalists hold that the sameness of phenomenal character in perception and hallucination is exhausted or constituted by this sameness in content (see Tye (2000), Byrne (2001)). But this latter claim is not essential to intentionalism (see the discussion of intentionalism and qualia below). What is essential is that the intentional content of perception explains (whether wholly or partly) its phenomenal character.

The intentional content of perception is sometimes called “perceptual content” (see the entry on the contents of perception). What is perceptual content? A standard approach to intentionality treats all intentional states as propositional attitudes: states which are ascribed by sentences of the form “S ___ that p” where ‘S’ is to be replaced by a term for a subject, ‘p’ with a sentence, and the ‘___’ with a psychological verb. The distinguishing feature of the propositional attitudes is that their content—how they represent the world to be—is something which is assessable as true or false. Hence the canonical form of ascriptions of perceptual experiences is: “S perceives/experiences that p”. Perception, on this kind of intentionalist view, is a propositional attitude (see Byrne (2001) for a recent defence of this idea, see also Siegel (2010)).

But intentionalism is not committed to the view that perception is a propositional attitude. For one thing, it is controversial whether all intentional states are propositional attitudes (see Crane (2001: Chapter 4)). Among the intentional phenomena there are relations like love and hate which do not have propositional content; and there are also non-relational states expressed by the so-called “intensional transitive” verbs like seek, fear, expect (see the entry on intensional transitive verbs). All these states of mind have contents which are not, on the face of it, assessable as true or false. If I am seeking a bottle of inexpensive Burgundy, what I am seeking—the intentional content of my seeking, or the intentional object under a certain mode of presentation—is not something true or false. Some argue that these intentional relations and intentional transitives are analysable or reducible to propositional formulations (see Larson (2003) for an attempt to defend this view of intensional transitives; and Sainsbury (2010) for a less radical defence). But the matter is controversial; and it is especially controversial where perception is concerned. For we have many ways of talking about perception which do not characterise its content in propositional terms: for example, “Vladimir sees a snail on the grass”, or “Vladimir is watching a snail on the grass” can be distinguished from the propositional formulation “Vladimir sees that there is a snail on the grass” (for an interesting recent discussion of watching, see Crowther 2009). There are those who follow Dretske (1969) in claiming that these semantical distinctions express an important distinction between “epistemic” and “non-epistemic” seeing. However, the view that perceptual content is non-propositional is not the same as the view that it is “non-epistemic” in Dretske’s sense. For ascriptions of non-epistemic seeing are intended to be fully extensional in their object positions, but not all non-propositional descriptions of perception need be (for example, some have argued that “Macbeth saw a dagger before him” does not entail “there is a dagger which Macbeth saw”: cf. Anscombe (1965)). The question of whether perception has a propositional content is far from being settled, even for those who think it has intentional content (see McDowell (2008); Crane (2009)).

Another debate about the content of perceptual experience—independent of the issue of whether it is propositional—is whether it is singular or general in nature (see Soteriou (2000); and for a more general discussion, see Chalmers (2006)). A singular content is one that concerns a particular object, and such that it cannot be the content of a state of mind unless that object exists. Singular contents are also called “object-dependent”. A general content is one whose ability to be the content of any intentional state is not dependent on the existence of any particular object. General contents are also called “object-independent”. Those who think (like Snowdon (1992), McDowell (1994), Brewer (2000)) that the content of perceptual experience can be expressed by a sentence containing an irreducible demonstrative pronoun (e.g., of the form “that F is G’) will also argue that the content of experience is singular; those who think (like Davies (1992) and McGinn (1989)) that the content of experience is general (e.g., of the form, “there is an F which is G”) are committed to its object-independence. It might seem that an intentionalist must say that the content of perception is wholly general. However, Burge (1991) has argued that any genuinely perceptual episode has an irreducibly singular element, even though the episode could share a component of content with a numerically distinct episode. Martin (2002) argues that the availability of this position shows that intentionalism could deny that the content of experience is wholly general.

The issue about whether the content of perceptual experience is singular or general is not simply about whether the existence of the experience entails or presupposes the existence of its object. An example will illustrate this. Suppose for the sake of argument that experience essentially involves the exercise of recognitional capacities, and I have a capacity to recognise the Queen. Let’s suppose too that this is a general capacity which presupposes her existence. It is consistent with this to say that I could be in the same intentional state when I am hallucinating the Queen, as when I am perceiving her. Although the capacity might depend for its existence on the Queen’s existence, not every exercise of the capacity need depend on the Queen’s presence. The capacity can “misfire”. Hence intentionalism can hold that experiences are the same in the hallucinatory and veridical cases, even though the existence of the involved recognitional capacity presupposes the existence of the object recognised.

The objects of intentional states are sometimes called “intentional objects” (Crane (2001: Chapter 1)). What are the intentional objects of perceptual experience, according to intentionalists? In the case of veridical perception, the answer is simple: ordinary, mind-independent objects like the churchyard, the snow (etc.) and their properties. But what should be said about the hallucinatory case? Since this case is by definition one in which there is no mind-independent object being perceived, how can we even talk about something being an “object of experience” at all here? As noted above, intentionalists say that experiences are representations; and one can represent what does not exist (see Harman (1990), Tye (1992)). This is certainly true; but isn’t there any more to be said? For how does a representation of a non-existent churchyard differ from a representation of a non-existent garbage dump, say, when one of those is hallucinated? The states seem to have different objects; but neither of these objects exist (see the entry nonexistent-objects).

One proposal is that the objects of hallucinatory experience are the properties which the hallucinated object is presented as having (Johnston (2004)). Another answer is to say that these hallucinatory states of mind have intentional objects which do not exist (Smith (2002: Chapter 9)). Intentional objects in this sense are not supposed to be entities or things of any kind. When we talk about perception and its “objects” in this context, we mean the word in the way it occurs in the phrase “object of thought” or “object of attention” and not as it occurs in the phrase “physical object”. An intentional object is always an object for a subject, and this is not a way of classifying things in reality. An intentionalist need not be committed to intentional objects in this sense; but if they are not, then they owe an account of the content of hallucinatory experiences.

How does the content of perceptual experience differ from the content of other intentional states? According to some intentionalists, one main difference is that perception has “non-conceptual” content. The basic idea is that perception involves a form of mental representation which is in certain ways less sophisticated than the representation involved in (say) belief. For example, having the belief that the churchyard is covered in snow requires that one have the concept of a churchyard. This is what it means to say that belief has conceptual content: to have the belief with the content that a is F requires that one possess the concept a and the concept F. So to say perception has non-conceptual content is to say the following: to have a perception with the content that a is F does not require that one have the concept of a and the concept F. The idea is that one’s perceptual experience can represent the world as being a certain way—the “a is F” way—even if one does not have the concepts that would be involved in believing that a is F. (For a more detailed version of this definition, see Crane (1998a) and Cussins (1990); for a different way of understanding the idea of non-conceptual content, see Heck (2000) and Speaks (2005). The idea of non-conceptual content derives from Evans (1982); there are some similar ideas in Dretske (1981); see Gunther (2002) for a collection of articles on this subject. Other support for non-conceptual content can be found in Bermúdez (1997); Peacocke (1992); Crowther (2006); for opposition see Brewer (2000) and McDowell (1994a)).

3.3.4 Objections to the Intentionalist Theory

Critics of the intentional theory have argued that it does not adequately distinguish perceptual experience from other forms of intentionality, and therefore does not manage to capture what is distinctive about experience itself. (McDowell (1994), Martin (2002), Robinson (1994: 164)).

One objection of this kind is that intentionalists can give no account of the qualitative or sensory character of perceptual experience. Experiencing something, unlike thinking about it, has a certain “feel” to it. Yet, the objection runs, intentionalism has no resources to deal with this fact, since it explains experience in terms of representation, and merely representing something need have no particular “feel” whatsoever. Believing that something is the case, for example, or hoping that something is the case, are both forms of mental representation, but neither state of mind has any “feel” or qualitative character to call its own. (Words or images may come to mind when mentally representing something in this way, but it is not obvious that these are essential to the states of mind themselves.) So the challenge is the following: if there is nothing about representation as such which explains the “feel” of an experience, how is experience supposed to be distinguished from mere thought?

There are a number of ways an intentionalist can respond. One is simply to take it as a basic fact about perceptual intentionality that it has a qualitative or phenomenal character (see Kriegel (2013)). After all, this response continues, even those who believe in qualia have to accept that some states of mind have qualia and some do not, and that at some point the distinction between mental states which are conscious/qualitative, and those which are not, just has to be accepted as a brute fact.

Another response is to say that in order to explain the phenomenal character of perceptual experience, we need to treat perception as involving non-intentional qualia as well as intentionality (see Peacocke (1983: Chapter 1); Shoemaker (1993); Block (1997)). There is, accordingly, a dispute between these intentionalists who accept qualia (like Block and Shoemaker) and those who don’t (like Harman (1990) or Tye (1992)). The first kind of intentionalist holds that in addition to its intentional properties, perceptual experience also involves qualia; the second kind denies this. (See the discussion of “the transparency of experience” in §1.1.3 above; and see Spener (2003)).

Consider the inverted spectrum argument (see the entry on inverted qualia). This argument is based on an ancient speculation: that it is possible that two people’s colour experience could vary massively and systematically and that this difference be undetectable from the third person perspective (see Shoemaker (1996)). For example, consider two people Alice and Bob, whose colour perceptions are inverted relative to one another. Whenever Alice sees something red, Bob sees something blue and vice versa. Yet Alice and Bob each call all the same things “red”, and arguably believe that all the same things are red (fire engines, poppies etc.). It can further be argued that the representational or intentional content of their belief that fire engines are red is derived from the representational content of their experiences of red fire engines, since this belief is a perceptual belief. What then explains their mental difference? Defenders of qualia say that what explains this is the difference in the qualia of their mental states. Alice and Bob are intentionally or representationally identical—they represent the world in the same way—they differ in the non-representational qualia of their experience. (Intentionalists who deny qualia will dispute this by saying that the difference between Alice and Bob is indeed a representational difference: see Tye (2000) and Hilbert and Kalderon (2000). For more on the inverted spectrum, see Block (2007), Egan (2006), Marcus (2006). For other arguments attempting to establish qualia, see Block (1997), (2010), Peacocke (1983)).

3.4 The Naive Realist Theory

3.4.1 The Naive Realist Theory

Consider the veridical experiences involved in cases of perception; cases where one genuinely sees or otherwise perceives an object for what it is. Like sense-datum theorists, and unlike intentionalists, naive realists hold that such experiences themselves consist of relations of awareness to objects. However, like intentionalists, naive realists reject sense-data and appeal instead to ordinary objects. So the naive realist holds, in contrast to both the sense-datum theory and intentionalism (and, adverbialism), that the veridical experiences involved in genuine cases of perception consist, in their nature, of relations to ordinary objects (Level 1). And this is put to work in explaining the phenomenal character of such experiences (Level 2). Take the churchyard covered in white snow and suppose one sees this for what it is. Why is this a case of things appearing white to one? Here the naive realist appeals to the real presence in the experience of the white snow itself. The character of one’s experience is explained by an actual instance of whiteness manifesting itself in experience.

For the naive realist, the character of the experience one has in seeing the churchyard for what it is is constituted in part by the whiteness of the snow itself and not by the representation of such whiteness where representation is understood as it is by the intentionalist: that is, where an experience’s representation of something as white is something which doesn’t require the presence of an actual instance of whiteness. And many naive realists describe the relation at the heart of their view as a non-representational relation. This means that many naive realists think of experience and its character as non-representational in this sense: (a) intentional content of the sort appealed to by the intentionalists to explain character is not appealed to, and (b) what is fundamental to experience is something which itself cannot explained in terms of representing the world: a primitive relation of awareness to aspects of the world.

But care is needed here, for two reasons. First, neither (a) nor (b) entail that experience is non-representational tout court, that experiences don’t have representational content. For one might think of experience as representational in a way that is not tied to explaining phenomenal character (for instance content might be needed to explain experience’s epistemic role). If one thought of experience as contentful in a way that is not tied to explaining character, that would not be to endorse intentionalism, nor would it be to reject (a) or (b). And second, McDowell (2013) seems to be a naive realist who rejects (b), for he thinks that experience is relational in virtue of being contentful in a certain way—a way which thus contrasts with the way in which experience is contentful on non-relational views such as intentionalism.  (For further discussion see the articles in Brogaard (2014)).

The most prominent form of naive realism invokes (a) and (b). Such naive realists assign an important explanatory role to the world itself, without the involvement of content, in explaining the character of veridical experiences. It would be a mistake, however, to think that such naive realists must think of veridical experiences as consisting just in a simple two-place relation between a perceiver and a worldly subject-matter whereby phenomenal character is constituted entirely by the presented subject-matter. This would mean that there could be no variation in the phenomenal character without a variation in the presented subject-matter. But naive realists admit that even holding fixed the presented subject-matter there can be variation in the character of experience. This is worked out in different (but compatible) ways by different theorists. One approach is to keep the simple two-place view, yet note how variations in the perceiver relatum can make for variations in the character of experience (Logue (2012)). Another is to highlight a third-relatum which encapsulates various conditions of perception such as one’s spatiotemporal perspective, perceptual modality, and other conditions of perception variation in which can make for variation in phenomenal character (Campbell (2009), Brewer (2011)). It makes sense to suppose that if a given experience is of a subject-matter from a certain viewpoint (Martin (1998)), or standpoint (Campbell (2009)), then variation in what goes into one having the particular viewpoint or standpoint one has should make for variation in the phenomenal character. And we also need to look at the relation of awareness itself. Many naive realists hold that there can be variation in the way or manner in which one is related to a subject-matter which makes a difference to phenomenal character (Soteriou (2013), Campbell (2014)). Thus naive realists will reject the transparency thesis as it is discussed in §1.1.3, specifically (ii).

Like intentionalists, naive realists want to maintain our ordinary conception of perceptual experience. They hold to both Awareness and Openness. Naive realists think that we are sometimes perceptually aware of ordinary objects: that’s what we have in veridical and illusory experiences (see §3.4.2). Such experiences are cases of such awareness. And perceptual experience satisfies Openness. In veridical and illusory experiences, the character of experience is a presentation of ordinary objects, and is immediately responsive to the character of such objects because such objects are literally involved in the experience, part constitutive of its character.

How, then, does the naive realist respond to the arguments which animate the Problem of Perception?

3.4.2 The Naive Realist Theory and The Argument from Illusion

There are various different approaches available to a naive realist here (see e.g., Fish (2009: Chapter 6), Brewer (2008, 2011: Chapter 5), Kalderon (2011), Genone (2014), Campbell (2014)). But one approach is to target the base case. Naive realists, like intentionalists, can reject the Phenomenal Principle: in illusions it appears to one as if something is F even though one is not aware of anything which is F. When one sees a white wall as yellow, what one is aware of is a white wall, and that is not yellow. So how does naive realism differ from intentionalism about illusions? In two respects: first, naive realists can group illusory experiences with veridical experiences to the extent that they think of them as fundamentally cases of non-representational relations of awareness to ordinary objects. Second, the naive realist can explain the character of such illusory experiences without appeal to intentional content, but instead by appealing to ordinary objects, and their features. On this second difference, one approach is that developed by Brewer:

visually relevant similarities are those that ground and explain the ways that the particular physical objects that we are acquainted with in perception look. That is to say, visually relevant similarities are similarities by the lights of visual processing of various kinds... very crudely, visually relevant similarities are identities in such things as the way in which light is reflected and transmitted from the objects in question, and the way in which the stimuli are handled by the visual system, given its evolutionary history and our shared training during development  (2011: 103)... in a case of visual illusion in which a mind-independent physical object, o, looks F, although o is not actually F, o is the direct object of visual perception from a spatiotemporal point of view and in circumstances of perception relative to which o has visually relevant similarities with paradigm exemplars of F although it is not actually an instance of F (2011: 105).

So though o may not itself be F, it can exist in certain conditions, C, such that it has visually relevant similarities to paradigm F things and in that sense it will objectively look F, or look like an F thing—that is, it will itself have a property, a look or an appearance, independently of anyone actually clapping their eyes upon it (see also Martin (2010), Kalderon (2011) and Genone (2014) on objective looks). If o is then seen in C, o itself will look F to one in perception. Brewer spells this all out in much more detail, and with various examples. One example is seeing a white piece of chalk as red. The chalk is seen in abnormal illumination conditions such that the white piece of chalk itself looks like a paradigm red piece of chalk—it has ’visually relevant similarities with a paradigm piece of chalk, of just that size and shape’ (2011: 106). Given that it is seen in those conditions, it looks red to one, even though it is not in fact red. Here, then, we have an account of illusions in which we appeal to objects and the ways those objects are, not the ways the are represented to be, in explaining character.

3.4.3 The Naive Realist Theory and The Argument from Hallucination

How does the naive realist deal with the argument from hallucination? The naive realist denies its conclusion (C) and unlike the intentionalist wants to deny (C) read as

(C*) veridical experiences are not fundamentally cases of perceptual awareness of ordinary objects.

They accept (A) and so block the argument by rejecting the spreading step (B) ((he Common Kind Assumption (CKA)). Suppose that, as the naive realist holds, when one sees a snow covered churchyard for what it is, one has an experience which is in its nature a relation between oneself and ordinary objects. Whatever an hallucinatory experience as of a snow covered churchyard is, it is not an event with that nature. For such a hallucination could occur quite apart from any relevant worldly items (e.g., in the lab of a scientist manipulating your brain, in a world with no white things). Instead of taking (B) and these facts about hallucinations as grounds to reject the supposition of naive realism, the naive realist instead gives up (B)/(CKA) and thinks of veridical experiences and hallucinatory experiences as of different fundamental kinds. (For a much more nuanced and detailed formulation of the naive realist thinking here, see Martin (2004), (2006)).

In blocking the argument from hallucination in this way the naive realist takes on a disjunctive theory. The theory was first proposed by Hinton (1973) and was later developed by P.F. Snowdon (1979, 1990), John McDowell (1982, 1987) and M.G.F. Martin (2002, 2004, 2006). Disjunctivism is not best construed as it is by one of its proponents, as the view “that there is nothing literally in common” in perception and hallucination, “no identical quality” (Putnam (1999: 152)). For both the perception of an X and a subjectively indistinguishable hallucination of an X are experiences which are subjectively indistinguishable from a perception of an X. What disjunctivists deny is that what makes it true that these two experiences are describable in this way is the presence of the same fundamental kind of mental state. Disjunctivists reject what J.M. Hinton calls “the doctrine of the ‘experience’ as the common element in a given perception” and an indistinguishable hallucination (Hinton (1973: 71)). The most fundamental common description of both states, then, is a merely disjunctive one: the experience is either a genuine perception of an X or a mere hallucination of an X. Hence the theory’s name.

But what support is there for the disjunctivist’s rejection of (CKA)? Some defenders of disjunctivism have claimed that there is a relatively simple argument against the (CKA). Putnam, for example, has argued that since the common kind is defined by subjective indistinguishability, and since subjective indistinguishability is not transitive, then it cannot define a sufficient condition for the identity of states of mind, since identity is transitive (Putnam (1999: 130)). The argument that subjective indistinguishability is not transitive derives from the so-called “phenomenal sorites” argument: the possibility that there could be a series of (say) colour samples, arranged in a sequence such that adjacent pairs were subjectively indistinguishable but that the first and last members of the series were distinguishable. Hence sample 1 could be subjectively indistinguishable from sample 2, and so on; and sample 99 could be subjectively indistinguishable from sample 100, but sample 1 nonetheless be subjectively distinguishable from sample 100. Those who want to defend (CKA) need, therefore, to respond to this argument; one way is to follow Graff (2001), and argue that the phenomenal sorites argument is in fact fallacious.

Taking a different approach, Martin (2002: 421) argues that each of the main theories of perception is an “error theory” of perception (in J.L. Mackie’s (1977) sense). That is, each theory convicts common sense of an error about perception: for example, the sense-datum theory convicts common sense of making the erroneous assumption that perception is a direct awareness of mind-independent objects. Against this background, Martin argues that abandoning (CKA) is the least revisionary position among all the possible responses to the Problem of Perception, and thus follows Hinton (1973) in holding the disjunctivist position to be the default starting point for discussions of perception. (A further approach is to be found in McDowell (2008) who attempts to support disjunctivism on epistemological grounds.)

3.4.4 Objections and The Development of Disjunctivism

Naive realism avoids the argument from hallucination by denying (CKA) and thus taking on disjunctivism. But some object to this and try to support (CKA) with a so-called causal argument

1. Introduction

The etymology of perception in Sanskrit underlines a major and, perhaps the most controversial, issue in classical Indian epistemology, viz. is the sensory core all there is to the content of a perceptual experience? Put differently, it is asked whether the content of a perceptual experience is restricted to being unconceptualized (nirvikalpaka), or can any part of it be conceptualized (savikalpaka) as well? The Naiyāyikas generally take perception to be a two-staged process: first there arises a non-conceptual (nirvikalpaka) perception of the object and then a conceptual (savikalpaka) perception, both being valid cognitions. For Buddhists, non-conceptual perceptions alone are valid, while Grammarians (Śābdikas) deny their validity altogether. Sāṃkhya and Mīmāṃsā agree with the Nyāya position. These two realist schools, Nyāya and Mīmāṃsā, contest the Grammarian as well as the Buddhist positions. Advaita Vedānta position on perception seems to agree, in spirit, with the Buddhists, but their reasons for supporting non-conceptual perceptions alone as ultimately valid (paramārthika satta) are very different. This debate, on the role of concepts in perception, is discussed in detail in section 3.

Yet another debate about the nature of universals and concepts looms in the background of this debate. How do we know universals or concepts? The Buddhist introduce the doctrine of apoha to provide the resources for constructing concepts from sensory content to further the nominalist project of explaining thought and language in a world of particulars. In response to Buddhist nominalism, Nyāya philosophers present a defense of realism in the course of which they argue for a theory of real perceivable universals. This debate will be the focus of secion 4.

A very critical question germane to these epistemological issues is raised by the Buddhist philosopher Vasubandhu (c. 4th century CE): how do we distinguish veridical perceptions from the non-veridical ones? This is taken up in the last section.

Before we start out with the definitions, the following observation may be noted. It is true that the classical Indian philosophers were seriously concerned with the notions of enlightenment, the highest good, freedom from the cycle of rebirth and the attainment of ultimate bliss, etc. Therefore, some even question whether they were concerned with any epistemological questions at all, much less the ones raised here? But they were! For Naiyāyikas, in particular, this was a major focus: the reason offered in the early Nyāya tradition, in Vātsyāyana's (c. 450–500 CE) commentary on the Nyāya-sūtra, is that without knowledge of objects there is no success in practical response to them. Not very enlightening, perhaps. However, a much sharper justification comes from Gaṅgeśa (c. 12th century CE), the founder of the Navya-Nyāya school, in the introduction to his great work, Jewel Of Reflection On The Truth(Tattvacintāmaṇi):

In order that discerning persons may have interest in studying the work, Akṣapāda Gautama (c. 2nd century CE) laid down the sūtra: ‘Attainment of the highest good comes from right knowledge.’.

It should not then be surprising that one of the most sophisticated classical Indian treatises dealing with perception, Kumārila's (c. 7th century CE) Pratyakṣapariccheda (a portion of Ślokavārttika pertaining to the fourth sūtra of Mīmāṃsā-sūtra), discusses the nature and validity of perception without any consideration of its role in the ascertainment of religious and moral truth; in fact, the Mīmāṃsā-sūtra itself characterizes perception as not being a means of knowing righteousness (Dharma). It is true that epistemological debates in classical Indian philosophy arose in the religio-philosophical context; however, there is plenty of evidence on record to show that classical Indian philosophers were haunted by the very same epistemological concerns that have troubled the minds of Western philosophers through the ages. The controversial classical Indian epistemology issue—whether perception is conceptualized or not?—continues to be debated in the Western and Indian philosophy journals even today. That said, what makes this historical inquiry significant is that the epistemological issues in classical Indian philosophy are introduced against the backdrop of radically different metaphysical and ethical presuppositions.

2. Perspectives on Perception

Most classical Indian philosophical schools accept perception as the primary means of knowledge, but differ on the nature, kinds and objects of perceptual knowledge. Here we first survey Buddhist and orthodox Hindu schools' definitions of perception (excluding Vaiśeṣika and Yoga schools since they simply take on board Nyāya and Sāṃkhya ideas, respectively) and note the issues raised by these definitions. As mentioned above, the orthodox schools generally accept both non-conceptualized (indeterminate) and conceptualized (determinate) perceptual states in sharp contrast to the Buddhist view that perception is always non-conceptualized or indeterminate awareness.

2.1 Buddhist nominalism

The oldest preserved definition of perception in the Buddhist tradition is the one by Vasubandhu (c. 4th century CE), “Perception is a cognition [that arises] from that object [which is represented therein]” (Frauwallner, 1957, p. 120). However, the more influential and much discussed view is that of later Buddhist Yogācāra philosopher Diṅnāga (c. 480–540 CE) for whom perception is simply a cognition “devoid of conceptual construction (kalpanāpodhaṃ)”. Taber (2005, p. 8) notes two important implications of this definition. First, perception is non-conceptual in nature; no seeing is seeing-as, because that necessarily involves intervention of conceptual constructs, which contaminate the pristine given. Perception is mere awareness of bare particulars without any identification or association with words for, according to Diṅnāga, such association always results in falsification of the object. Referents of the words are universals which, for the Buddhist, are not real features of the world. Second, Diṅnāga's definition only indicates a phenomenological feature of perception; it says nothing about its origin and does not imply that it arises from the contact of a sense faculty with the object. Therefore, for the Buddhist idealist, the object that appears in perceptual cognition need not be an external physical object, but a form that arises within consciousness itself. Both these ideas led to vigorous debates in classical Indian philosophy between the Hindus and the Buddhists. The first of these ideas relates to the notion of non-conceptual perception, the second to idealism. Diṅnāga's philosophy is idealist-nominalist in spirit and his epistemological position is in sync with the Buddhist metaphysical doctrines of no-self and evanescence of all that exists which, expectedly, evoke strong reaction from the realist Nyāya-Vaiśeṣika and Mīmāṃsā schools.

In recent literature, there has been a scholarly debate on whether the Indian Yogācāra philosophy is a form of idealism or not. This debate is murky because there are various versions of idealism discussed in the literature in Buddhist philosophy. At least three versions have been discussed in recent literature in Buddhist philosophy: subjective idealism (the view that there are no mind-independent objects); metaphysical idealism (the view that external objects do not exist); and, epistemic idealism (the view that what we are immediately aware of is intrinsic to cognition). Lusthaus (2002) and Coseru (2012) have argued, respectively, for a "phenomenological" and "phenomenalist naturalist" interpretation of Yogācāra in opposition to the standard idealist interpretation. The main argument for the phenomenological reading is that the epistemic claims made by the Yogācāra philosophers do not commit them to ontological claims. This would avoid the charge of metaphysical idealism but is still open to being interpreted as offering an epistemic or subjective idealism. Lusthaus sees Yogācāra philosophers' denial of solipsism and affirmation of other minds as a fatal blow to the idealist interpretation of Yogācāra. Idealism does not necessitate solipsism as is made clear in Berkeley's version of subjective idealism and Hegel's absolute idealism which explicitly requires other minds. Thus, there is reason to think that the idealist interpretation of Yogācāra is not threatened by its commitment to other minds. It is not entirely clear whether Coseru's phenomenalist view involves a denial of idealism or he thinks that it is compatible with an idealist reading of Yogācāra.

More recently, Kellner and Taber (2014) have presented a new reason for the revival of the standard idealist reading of Yogācāra. Their argument for this reading is based on Vasubandhu's argumentative strategy rather than the logical structure of individual proofs. They claim that in the Viṃśikā Vasubandhu uses the argument from ignorance, according to which, the absence of external objects is derived from the absence of evidence for their existence. They also note that Vasubandhu uses the same strategy to refute the existence of the self in the Abhidharmakośabhāṣya IX. The argument from ignorance seems like a bad strategy. It is often listed as a logical fallacy of the general form: since statement P is not known or proved to be true, P is false. But because the general form of the argument is bad, it does not necessarily follow that every argument of that form is unsuccessful. It may well succeed because of other features, for example the semantic meanings of the terms or when the arguments are arguments to the best explanation. Kellner and Taber emphasise that some arguments from ignorance are successful when they function as arguments to the best explanation especially in contexts where there are agreed-upon standards of verification. For example, the medical community agrees that the most accurate and sensitive test for typhoid is testing the bone marrow for Salmonella typhi bacteria. If it turns out that it cannot be proven that one has typhoid (because of the lack of Salmonella typhi bacteria in one's bone marrow), then it is false that one has typhoid. No matter how suggestive the symptoms are, if the specific bacteria do not show up in the bone marrow within a specific time period, then one does not have typhoid. So, then, the question is: Is Vasubandhu's argument from ignorance successful for establishing idealism? I fear not. That is because there are no universally agreed-upon criteria among Classical Indian philosophers (not even among fellow-Buddhists) as to what counts as evidence for the existence of external things.

2.2 Nyāya realism

The most comprehensive, and the most influential, definition of perception in classical Indian philosophy is offered in Gautama's Nyāya-sūtra 1.1.4:

Perception is a cognition which arises from the contact of the sense organ and object and is not impregnated by words, is unerring, and well-ascertained.

Expectedly, each part of this definition has raised controversy and criticism. If perception is a cognition (and non-erroneous), then it is a state of knowledge, rather than a means to knowing! How does that constitute a primary means of knowledge? Some Naiyāyika commentators, Vācaspati Miśra (c. 900–980 CE) and Jayanta Bhaṭṭa (c. 9th century CE) among them, suggest that the sūtra is to be understood by adding to it the term ‘from which (yataḥ),’ since the preceding sūtra-s indicates that Gautama's formulation of this sūtra was intended to define the instrument of a valid perceptual cognition. Another issue has been the interpretation of the word “contact”. In what sense are the eye and the ear, the sense organs for vision and auditory perception, respectively, in contact with their objects? Here a careful look at the term “sannikarṣa,” generally translated as contact, helps resolve the issue; “Sannikarṣa” literally means ‘drawing near,’ and can be interpreted as being in close connection with or in the vicinity of. Thus perception is that which arises out of a close connection between the sense organ and its object.

More substantial debates on the nature of perception focus on the adjectives in the latter part of the sūtra, viz., non-verbal (avyapadeśyam), non-erroneous or non-deviating (avyabhichāri), and well-ascertained or free from doubt (vyavasāyātmaka). There is some disagreement among the Naiyāyika commentators about the interpretations of the adjectives non-verbal and well-ascertained. Vātsyāyana, in his commentary on the Nyāya-sūtra, argues that the adjectives non-verbal and well-ascertained are really part of the definition; non-verbal to point out that perceptual knowledge is not associated with words (Bhartṛhari, the famous Grammarian, on the other hand, holds that awareness is necessarily constituted by words and apprehended through them) and well-ascertained to affirm that perceptual knowledge is only of a definite particular and specifically excludes situations in which the perceiver may be in doubt whether a perceived object ‘a’ is an F or a G. Vācaspati Miśra, argues that the adjective well-ascertained need not be used to exclude the so-called perception in the form of doubt, as doubtful knowledge, being invalid, is already excluded by the adjective non-erroneous. Rather, the term vyavasāyātmaka stands for determinate perceptual judgment. Thus understood, the adjectives non-verbal and determinate seem to be complementary; a piece of non-verbal perceptual knowledge cannot be said to be, at the same time, determinate. Vācaspati Miśra posits that these two adjectives indicate two different forms of perceptual cognition and are not to be regarded as its defining characteristics. According to him, Gautama included these adjectives to identify two kinds of perceptual knowledge: avyapadeśyam indicates non-conceptual or non-verbal perception and vyavasāyātmaka indicates conceptual or determinate perceptions. He contends that by the term non-verbal, Gautama refutes the Grammarian view and includes non-conceptual perception and, by the term well-ascertained, he refutes the Buddhist view and includes conceptual or judgemental perceptions as valid. Pradyot Mondal (1982) traces the history of this controversy among Naiyāyikas. He offers overwhelming scholarly evidence in favor of the view that Naiyāyikas mostly regard the adjectives as part of the definition of perception and do not agree with Vācaspati's interpretation. For most Naiyāyikas “non-verbal” is included to deny the causal role of words in origination of perceptual cognition and, therefore, it applies to non-conceptual and conceptual perceptions both, the difference being that the former is inexpressible in language, while the latter is not. Thus Mondal claims that the adjective “non-verbal” is sufficient on its own to reject the Grammarian and the Buddhist views of perception. “Non-verbal” has raised a most contentious debate, for over a millennium, between Nyāya and Buddhist philosophers, and it is still alive today. The role of concepts in perception—in dispute in this debate—will be discussed in the next section.

The Navya-Naiyāyika Gaṅgeśa objects to the notion ‘sensory connection’ in the classical Nyāya definition of perception, arguing that this makes the definition too wide and too narrow at the same time: too wide because it implies that every awareness is perceptual being produced by virtue of a connection with the ‘inner’ sense faculty or mind (manas); too narrow because it fails to include divine perception, which involves no sensory connection. Gaṅgeśa offers a simpler definition of perception as an awareness which has no other awareness as its chief instrumental cause. Being concerned that his definition may be interpreted as ruling out conceptualized or determinate perception that may have non-conceptual or indeterminate perception as one of it causes, he argues that indeterminate perception can never be the chief instrumental cause of determinate perception, although it is a cause, since it supplies the qualifier or the concept for determinate perception.

2.3 Mīmāṃsā realism

The PurvaMīmāṃsā-sūtra (MS) were originally composed by Jamini around 200 BCE. The fourth MS 1.1.4 says:

The arising of a cognition when there is a connection of the sense faculties of a person with an existing (sat) object—that (tat) is perception; it is not the basis of the knowledge of Dharma, because it is the apprehension of that which is present. (Taber, 2005:44)

There is no consensus among Mīmāṃsā commentators on whether this is intended as a definition of perception, even while an initial reading of it suggests that it may be. Kumārila, the noted Mīmāṃsā commentator argues that the first part of the sūtra is not intended as a definition because of the context in which it figures; the sūtra-s preceding it are concerned with an inquiry into righteousness (Dharma). Moreover, the sūtra construed as a definition of perception, results in too wide, and not too accurate, a definition, because it only says that perception arises from a connection between the sense faculty and an existing object and does not exclude perceptual error or inferential cognition. Taber (2005, 16), on the other hand, suggests that it is possible to construe MS 1.1.4 as a valid definition, and indeed such a construal was proposed by an earlier commentator, the so-called Vṛttikāra quoted at length by Śābara in his Śābarabhāṣyam. This, the most extensive commentary on the Mīmāṃsā-sūtra, suggests that the words of the sūtra (tat = ‘that’ and sat = ‘existing’) be switched around for a different reading for the first part of the sūtra, which would then state that, “a cognition that results from connection of the sense faculties of a person with that (tat) [same object that appears in the cognition] is true (sat) perception”. This switch rules out perceptual error and inference; both these present objects other than those that are the cause of the perception.

2.4 Sāṃkhya definition

In the oldest Sāṃkhya tradition, perception is the functioning of a sense organ. This is clearly inadequate, as the ancient skeptic Jayarāśi Bhaṭṭa (c. 8th century CE) is quick to point out. Perception in this sense cannot be a means of knowledge (pramāṇa) as it does not distinguish between proper and improper functioning of sense organs and, therefore, between valid and erroneous perceptions. A more sophisticated definition is later devised wherein perception is “an ascertainment [of buddhi or intellect] in regard to a sense faculty (Sāṃkhyakārikā 5 in Yuktīdipikā)”. This implies that perception is a modification of the intellect in the form of selective ascertainment of an object, brought about by the activity or functioning of a sense faculty. In some respects, this characterization of perception as an “ascertainment” of the intellect neatly captures the idea that perception, being an instrument of knowledge, is the primary means of knowledge. Ascertainment residing in the intellect is regarded as the instrument of perception, while residing in the self it is regarded as the result of the process of perception. Furthermore, the Sāṃkhyakārikā states that the function of the senses with regard to the objects is “a mere seeing” (Sāṃkhyakārikā, 28b), and the function of the intellect, referred to as ascertainment, can be thought of as “identification” of the object as in “this is a cow”, etc. (Sāṃkhyakārikā 5ab). This suggests a two-stage process: first the functioning of the sense faculty results in “mere seeing” of the object (non-conceptualized awareness) and, later this mere seeing is acted upon by the intellect or mind and results in a conceptual identification of the object. This two-stage process is very similar to the detailed account of conceptual (savikalpaka) perception offered by the Mīmāṃsakas and the Naiyāyikas.

2.5 Advaita Vedānta: direct knowledge

According to Advaita Vedānta the defining characteristic of perception is the directness of knowledge acquired through perception (Bilimoria, 1980:35). In highlighting the directness of the perceptual process, the Advaitin differs from Nyāya and Mīmāṃsā proponents for whom the contact of the sense faculty with its object is central to the perceptual process. Vedānta Paribhāṣā (ed. 1972: 30) cites pleasure and pain as instances of perception that are directly intuited without any sense object contact. For the Advaitin perception is simply the immediacy of consciousness; knowledge not mediated by any instrument (Gupta et. al., 1991, p. 40). It is worth noting that this definition is very close to that accepted by Navya-Naiyāyikas. Like the latter, the Advaitins regard the role of the sensory connection as accidental, rather than essential, to the perceptual process. The Neo-Advaitins accept the distinction between conceptual or determinate perception (they refer to it as viṣayagata pratyakṣa) and non-conceptual or indeterminate perception (nirvikaplapkapratyakṣa), but do not think of non-conceptual perception as simply a prior stage of conceptualized perception, as other Hindu schools do.

3. Nirvikalpaka and Savikalpaka Pratyakṣa

The Sanskrit term kalpanā is variously translated as imagination or conceptual construction and is meant to be the source of ‘vikalpa’, roughly translated as concepts, but which may stand for anything that the mind adds to the ‘given’. The time-honored differentiation of perception into conception-free perception (nir-vikalpa pratyakṣa) and conception-loaded perception (sa-vikalpapratyakṣa) is made on the basis of concepts (vikalpa) (Matilal, 1986: 313).

3.1 The basis of Buddhist nominalism

The distinction between non-conceptual and conceptual was first drawn by Diṅnāga who contended that all perception is non-conceptual because what constitutes seeing things as they really are must be free from any conceptual construction. The claim is that a verbal report of proper perception is strictly impossible, for such a report requires conceptualization, which is not perceptual in character; the objects of conceptual awareness are spontaneous constructions of our mind and are essentially linguistic in character. On the other hand, what is seen, ‘the given’, does not carry a word or a name as its label and neither is such a label grasped along with the object, nor inherent in it, nor even produced by it; objects-as-such, the real particulars (svalakṣaṇas), do not, as Quine would say, wear their names on their sleeves. Furthermore, the sense faculty cannot grasp a concept or a name; if I have never smelt garlic before I first encounter it, I cannot smell it as garlic, though I can smell IT; an olfactory awareness can only grasp a smell present in the olfactory field. The Buddhists argue that a perceiver apprehends only the real particulars, arbitrarily imposes concepts/words on them and believes, mistakenly, that these are really there in the objects and integral to them. The conceptual awareness conceals its own imaginative quality and, because it results directly from experience, the perceiver takes it to be a perceptual experience. The perceiver fails to notice that imagination is involved and mistakenly thinks that he really perceives the constructed world. From the Buddhists standpoint, therefore, a perceiver can only perceive real particulars so that any perceptual experience is always and only at the non-conceptual level.

3.2 The development of Hindu realism: the Nyāya mission

The Nyāya view evolves in response to Buddhist account of perception. They regard perception as a cognitive episode triggered by causal interaction between a sense faculty and an object. This interaction first results in a sensory impression, nothing more than mere physiological change. This preliminary awareness, non-conceptual perception, is a necessary first step in the process of perception and is invariably followed by a structured awareness leading to conceptual perception. A cognition that is independent of preliminary sensory awareness cannot result in a perceptual judgment. The first awareness does not destroy the perceptual character of the second; rather, it facilitates this subsequent awareness. Non-conceptual perception is an indispensable causal factor for generation of conceptual perception, although memory, concepts and collateral information may also be required. It is important to note that the Nyāya notion of vikalpa (in their distinction of nir-vikalpa and sa-vikalpa) is different from that of the Buddhists. Unlike the latter, the Naiyāyikas do not think of vikalpa-s as mental creations or imaginative constructions but as objectively real properties and features of objects. Vikalpa in this sense indicates the operation of judging and synthesizing rather than imagining or constructing. Thus conceptual perceptions truly represent the structure of reality. Of the five types of concepts (vikalpa-s) recognized by the Buddhists, viz. nāma (word), jāti (universal), guṇa (quality), kriyā (action) and dravya (substance), the Naiyāyikas, regard all but the first vikalpa as categories of reality (Mondal, 1982, p. 364). Unlike the Grammarians, the Nyāya schools do not accept the objective reality of words; words are not inherent to the object presented in perception. Rather, the Naiyāyikas hold that the relation between word and object is created by convention in a linguistic community. Although a concept is associated with a word (nāma-vikalpa) by means of a convention, it is not merely a fabrication. For example, when someone brings garlic clove near my nose and teaches me by pointing to it that it is called garlic, then subsequently confronted with the garlicky odor and a similar clove, I can see it and smell it as garlic. Thus perceptual awareness includes knowledge of words but, insofar as it is perceptual awareness, it is brought about by sensory contact with the object and, its properties which exists independently of words.

The Buddhists reject this argument on the basis that the conventional meaning of a word relates the word with the concept or the universal. Universals or concepts cannot be objects of our perception; they cannot be sensed. Universals, attributes and concepts are theoretical constructs for the Buddhists; what is sensed is the actual object, the exclusive particular, the ultimate existent. The Buddhists offer two arguments in favor of the claim that only particulars are real. First, knowledge by means of words or verbal testimony is very different from perceptual knowledge, for what we are aware of when we hear the words “garlic is pungent” is very different from what we are phenomenologically aware of when we smell garlic; words do not denote or stand-in for actual objects and can be uttered in the absence of any objects, but perception cannot arise in the absence of objects. Second, the particulars are real or existent because they have causal efficacy (arthakriyāsāmarthya). Only particular real garlic can flavor one's food or ruin it, but the universal garlichood cannot do any of these; in this sense, only the particulars are real for they fulfill the purposes (artha) of humans.

The foregoing discussion shows that the epistemological debate between the Buddhists and the Naiyāyikas regarding the nature of perception rests on, and brings to the fore, their metaphysical disagreement about the nature of universals. The Naiyāyikas are realists about universals; universals are objective features of the world that impress themselves upon minds; they are not mere figments of our imagination. The Naiyāyikas hold that particulars are qualified propertied wholes and we directly perceive them as they are, without any kind of manipulation or imposition; we do not impose universals on property-less real particulars, rather we find stable, durable, relational wholes in reality that do not require any imposition or manipulation. They argue that there is no evidence of a world of bare particulars, as claimed by the Buddhists. Therefore conceptual or determinate perception does not involve distortion of reality; rather it presents things as they really are. To see a piece of sandalwood as it really is, we do not need to see the sandalwood as a colorless, odorless pure particular; indeed, since the piece of sandalwood is really brown and really fragrant, to see it as a propertied whole is to see it as it reallyis.

The idea that the world consists of propertied particulars seems to put pressure on the notion of non-conceptual perception. If there are no indeterminate particulars, what is the object of indeterminate perception? Indeed some Navya-Nyāya thinkers hold that the raw data of perception (‘real particulars’ in the Buddhists sense) is too inchoate and elusive to count as objects of knowledge. Recently, Arindam Chakrabarti (2000), a prominent contemporary Navya-Nyāya thinker offered seven reasons for altogether eliminating non-conceptual, or immaculate perceptions as he calls them, from Nyāya epistemology in an attempt to understand the “deeper relation between direct realism and concept-enriched perception”. Chakrabarti's skepticism about non-conceptual perception as a cognitive state stems from the fact that we cannot assign an intentional role to the object of indeterminate perception because the object of non-conceptual perception is incapable of being apperceived or directly intuited in any fashion. Chakrabarti's gauntlet has been picked by several Nyāya enthusiasts (Phillips, 2001 and 2004; Chadha, 2001, 2004 and 2006) and defenders of Buddhist doctrine (Siderits, 2004). This debate brings to the fore an important feature of non-conceptual perception first highlighted by Gaṅgeśa, suggesting that while there is no direct, apperceptive evidence for non-conceptual perception, it is posited as the best explanation for the availability of the qualifier (property, feature), since the cognizing subject is not immediately aware of the object of non-conceptual perception. Phillips (2001, p.105) presents Gaṅgeśa's argument for the inclusion of non-conceptual perception as an essential part of Nyāya epistemology:

…it [nirvikalpa pratyakṣa] is posited by the force of the following inference as the first step of a two step argument. “The perceptual cognition ‘A cow’ (for example) is generated by a cognition of the qualifier, since it is a cognition of an entity as qualified (by that qualifier appearing) like an inference”. The second step takes a person's first perception of an individual (Bessie, let us say) as a cow (i.e., as having some such property) as the perceptual cognition figuring as the inference's subject (pakśa) such that the cognizer's memory not informed by previous cow experience could not possibly provide the qualifier cowhood. The qualifier has to be available, and the best candidate seems to be its perception in the raw, a qualifier (cowhood), that is to say, not (as some are wont to misinterpret the point) as divorced from its qualificandum (Bessie) but rather as neither divorced nor joined, and, furthermore, not as qualified by another qualifier (such as being-a-heifer) but rather just the plain, unadorned entity. In the particular example, the entity is the universal, cowhood, or being-a-cow, although, again, it would not be grasped as a universal. Or as anything except itself.

The Navya-Nyāya notion of non-conceptual perception differs from that of the Buddhists in many respects, two of which are very important. First, according to Navya-Naiyāyikas, there is no apperceptive evidence for non-conceptual perception, unlike the Buddhists who contend that conception-free awareness is necessarily self-aware. The Navya-Naiyāyikas, as is obvious from the quote above, emphasize that the evidence for a non-conceptual sensory grasp of universals comes in the form of an inference. Second, according to Navya-Nyāya, the object of non-conceptual perception is a qualifier (concept), although not given as that in the first instance, but not a bare particular as the Buddhists hypothesize. It is, as the above quote explains, posited by the force of an inference; the ‘bare object’ of non-conceptual perception becomes the qualifier in a resultant determinate perception. While this does not satisfactorily address Chakrabarti's concern that lack of apperceptive evidence implies that the subject cannot assign an intentional role to the object of non-conceptual perception, Chadha (2006) argues that the subject's not being in a position to assign an intentional role to the object of non-conceptual perception is no hindrance to the intentionality of non-conceptual perception itself. Non-conceptual perception is awareness of a “non-particular individual” (Chakrabarti, 1995) and can be assigned the intentional role of a qualifier in virtue of the recognitional abilities acquired by the subject on the basis of the perceptual episode. The subject sees a non-particular individual but, since there is no apperceptive or conscious awareness, the subject does not see it as an instance of a universal or a qualifier. Chadha explicates Gaṅgeśa's insight that a qualifier is given as a non-particular individual, neither divorced from nor joined to the qualificandum and, therefore it is wrong to suggest that lack of apperceptive evidence implies that non-conceptual perception is not an intentional perceptual state.

3.3 The Mīmāṃsā advance in realism

Kumārila argued against the Buddhist position to show that perception is not always devoid of concepts. In Pratyakṣapariccheda, he principally targets Diṅnāga's theory, while simultaneously addressing some of Dharmakīrti's ideas and arguments. Kumārila, like Naiyāyikas, holds both the two kinds of perception as valid. For him the initial non-conceptualized perception is borne of the undifferentiated pure object (śuddhavastu) and is comparable to the perception of an infant and others who lack a language. The ‘pure object’ is the substratum for the generic and specific features of the object, but the subject is not distinctly aware of any of these and simply cognizes the object as an indeterminate particular, as “this” or “something”. Although Kumārila agrees with the Buddhists that the object of immediate perception is inexpressible in language, he maintains that it is different, in at least one respect, from the real particular (svalakṣaṇa) of the Buddhists; the latter being a structure-less unitary whole, whereas the former is non-unitary and grasps both the particular and the universal aspects of the object. Otherwise, Kumārila argues, it could not give rise to conceptual awareness, which explicitly identifies such features. Diṅnāga's counterpoint to this is that conceptual awareness at second stage cannot be a perception, since it involves application of concepts and words which, in turn, requires memory. If we admit conceptual awareness as perception, we are forced to accept that a sense faculty is capable of remembering (since perception is a cognition brought about by the functioning of the sense faculty) but that cannot be the case because a sense faculty, being a mere instrument of cognition, is in itself unconscious and cannot remember anything. Kumārila admits that conceptual awareness is aided by memory and concepts, but argues that that does not rob it of its perceptual character for the sense faculty is still functioning while in contact with the very same object. He further suggests that we should not expect a perceptual cognition to arise as soon as there is contact between a sense faculty and its object. He uses the analogy of entering a dimly lit room after walking in the blazing sun; even though the contents of the room are directly available to the sense faculties of the subject who has just walked in, he does not immediately apprehend the objects in front of him. However, the subject may become distinctly aware of the objects in the room and their features in the following moments. The perceptual character of the latter awareness is maintained so long as the connection between the sense faculty and the object is intact, even when other conceptual awarenesses or memories intervene between the initial contact with the object and the subsequent awareness. A conceptual awareness can be referred to as a perception even though the mind, qua memory, is involved because the functioning of the sense faculty is the factor responsible for arising of the awareness. Furthermore, he insists that the mind must be involved in all perceptions since it functions as a link between the sense faculty and the self; the sense faculty is turned on or activated by a connection with the self and, the self as the subject of knowledge is involved in all cognitions. He points out that even Buddhists do not deny this, since they hold that self-reflexive awareness accompanies every cognition. He contends that the Buddhists are wrong to insist that only a cognition arising directly from the functioning of a sense faculty is perception; they agree that we perceive inner states, e.g., pleasure and pain, and if the mind is accepted as the operative sense faculty in the self-reflexive awareness of such cognitions, it follows that they should admit that the mind is also the sense faculty that gives rise to conceptualized cognitions. He, however, clarifies that not every cognition that follows a contact between a sense faculty and an object is a perception, for if one were to open one's eyes momentarily (in the above analogy) and construct a judgment such as “that was table” with eyes closed again, it would not be a perceptual cognition since it solely depends on the memory of a fleeting sensory contact.

Later, Dharmakīrti, using a methodology very different (and akin to proof by contradiction) from his predecessor Diṅnāga, raises new problems for the Nyāya-Mīmāṃsā view. Assuming, he says, for the sake of the argument, that universals are real. Then the judgments “This is a cow,” “It is an animal,” relate two distinct entities, namely a particular (or object) and a universal (or concept) arguably via a non-relational tie as in being substratum and superstratum, with the proviso that the substratum object has the power to let the universal reside in it. This leads to all the universals (such as cowness, animalhood, etc) then being tied to the object by this simple and single power. In such a scenario, any perceptual judgment involving the universal cowhood as in the case of “This is a cow” makes subsequent judgments “This is an animal,” “This is a substance,” etc., superfluous. For, if one perceives an object along with its power to let any one universal reside in it, one must be able to perceive its power to attract all other universals that reside in it. Thus, there would be no distinction between “This is a cow” and “This is a substance”; clearly an unacceptable thesis. Matilal (1986, p.326) notes two points in connection with this argument. First, Dharmakīrti assumes that an object, or a unique particular, is perceived in its entirety and no part of it is left unperceived. Second, the realist has objectified all the universals including the relation-universal. If, as the realist believes, the object of perception—the particular—has the power to accommodate all universals in it, then the onus is on him to show why only a single universal manifests itself in a perceptual judgment. This concern is pertinent, especially against the Nyāya philosophers who admit only one single relation-universal: inherence, which supposedly unites all nesting universals with the object. The Naiyāyikas readily respond to this argument by pointing out that the redundancy objection rests on Dharmakirti's assumption that an object is grasped in its entirety in perception. This assumption is false; perception is perspectival, we never see all sides of an ordinary three-dimensional object, but we still see it.

Furthermore, Dharmakīrti's argues that conceptual or judgmental awareness is phenomenologically distinct from non-conceptual awareness. In the latter we are confronted with the object of perception which is vivid and immediate, while in the former no object is present. In the judgment “this is a cow”, even the ‘subject’ of the judgment does not refer to the object of perception, since words do not refer to perceived particulars but to universals which extend across space and time. Dharmakīrti admits that the words we apply to things have some objective basis in those things; we call something a cow because it has a certain effect, it gives milk, is gentle, or it calls forth a certain cognition, etc. This effect, in turn, inclines us to associate the word ‘cow’ with other things that have the same effect and we do that by jointly dissociating them from things that lack that effect. Universals, according to the Buddhists are arbitrarily constructed “exclusions” (apoha); words serve the purpose of separating things off from other objects. For example, the word ‘cow’ singles out a class of things by excluding them from things they are not, all things assembled together under the concept “cow” are distinct from each other and do not share a single nature that the word ‘cow’ names. A conceptual awareness insofar as it imputes a word to a particular object and, therefore a universal nature it shares with all others of the same universal-kind, essentially falsifies the object. Kumārila objects to the Buddhists theory of universals (apoha) on the grounds that it is counterintuitive and circular. The theory of universals (apoha) contradicts our intuition that meaning of a positive word is positive; there is nothing negative about the word ‘cow’. A negative entity can be the meaning of a word only where something is negated. Moreover, if we accept that understanding x requires eliminating non-x, then in turn we presuppose knowledge of non-x, which entails an understanding of non-non-x, and so on (Drefyus, 1997, p.215). The Mīmāṃsakas also take on board the concerns raised by the Naiyāyika philosopher Uddyotakara (c. 7th century CE), who questions the theory of exclusions on the specific grounds that it fails to offer an adequate theory of reference and relation between concepts and reality. He argues if the word ‘cow’ primarily designates a negative entity, either this entity is a cow in disguise or is different from a cow. If it is a cow in disguise then the Buddhist view of universals is no different from the Nyāya common sense realism that words are used to single out phenomena in the world. If the negative entity is different from a cow, then the word ‘cow’ does not refer to real cows, making it difficult to explain how any word can refer to real objects or classes thereof. This last point begs the question because the Buddhist denies that words refer to the objects in the real world. For him words refer to universals, and that is precisely what the world does not contain. The onus is put back on the realists to show that universals, which serve as meanings of words, are real properties of objects rather than imagined or mentally constructed features. This challenge is taken up by the Naiyāyikas and their position against the nominalist stand of both the Buddhists and the Grammarians is presented later below.

3.4 The Śābdika (Grammarian) nominalism and realist objections

Bhartṛhari, the most notable Grammarian, highlights the intimate relation between language, thought, and knowledge. Two aspects of his theory have important implications for the nature of perceptual experience. First, there is no non-linguistic cognition in the world; all knowledge appears permeated by words. Though Bhartṛhari's theory may leave room for extraordinary, or other-worldly, cognitions, there is no scope for pure non-conceptualized perception in this world. The essence of his theory is: words do not designate objects in the external world directly, but through the intervention of universals, which are inherent in words. Thus universals constitute the basis of our knowledge of the external world, since they are intimately connected with language and mind on the one hand, and the world on the other. Given this, the Grammarians question the very possibility of non-conceptual perception? The second aspect is underscored by Kumārila who ascribes the so-called Superimposition Theory to Bhartṛhari (Taber, 2005, p.27), according to which, a word has its “own form” superimposed upon its meaning. This has implications for determinate conceptual perception, which (for the pluralists and direct realists of Mīmāṃsā and Nyāya persuasions) arises purely out of the object itself and involves discrimination and determination of its nature.

Bhartṛhari's argument can be thought of as an attack, on the adjective ‘non-verbal’ (avyapadeśyam) in the Nyāya definition of perception, aimed at their belief that for cognitive comprehension language is an inessential detail. For him, bare sense-impressions cannot count as awarenesses because they are nor effective enough, nothing is accomplished by them and, they do not result in appreciable mental activity. Bhartṛhari gives an example: a man walking along a village path to approach his house would invariably touch some grass on the road, and in some sense this would be tactile awareness at a pre-linguistic level (Vākyapadīya, Ch.1, verse 123). But this would not count as an awareness unless combined with the further ability to sort it out or verbalize it; consciousness cannot reveal an object to us unless we discriminate it, and the process of discrimination requires verbalization. What about a baby's awareness, or that of a mute person, asks Vātsyāyana? Bhartṛhari points out that a baby's sensations or a mute person's awarenesses may still count as cognitive because they are linguistically potent. A pre-linguistic state of an infant can be cognitive if and only if it has speech potency, which is the cause of verbal language. So also, in the non-conceptual perceptual awareness (in adults and even some animals) speech-potency is latent; it is an essential trait of human consciousness and the defining characteristic of cognitive awareness (Vākyapadīya, Ch.1, verse 126). All knowledge of what is to be done in this world depends on speech-potential; even an infant has such knowledge due to residual traces from previous births (Vākyapadīya, Ch.1, verse 121). The initial sensory awareness of external objects which does not grasp any special features of them, nonetheless illuminates them in a non-specific manner as mere things by such expressions as ‘this’ or ‘that’ (Bhartṛhari; 123 and 124). Thus, insofar as the initial sensation is an awareness, it can be verbalized. The following analogy is offered as an argument for positing the presence of speech-seed (verbal disposition, as some modern philosophers call it) in pre-linguistic awareness: think about the experience of trying, but failing, to remember a verse heard before. Bhartṛhari claims that the entire verse exists in the cognitive faculty as speech-potency but because of lack of other contributory factors there is no verbalization. Similarly, a non-linguistic experience of a mute-person is an awareness because of the presence of verbal disposition or speech-seed even though there is no actualization of speech. There are no non-conceptual perceptions, because ordinary objects are not given to us without a concept (vikalpa) or some mode of presentation; verbalization makes the concept explicit. There are infinite concepts associated with an object, none integral to it. However, we always perceive an object in a concept as an instantiation of a universal; it is a cow, white, bovine, four-legged, etc. The point to note is that concepts or universals (vikalpa-s) are word-generated and superimposed on the objects; there are no ‘thing-universals’ or real universals over and above these. Bhartṛhari's defends linguistic nominalism, according to which, words are the only universals that exist; thing-universals are word-generated illusions. As Matilal remarks, for Bhartṛhari there is not much of a distinction between words and concepts, they are two sides of the same coin (Matilal, 1986, 396).

Naiyāyikas and Mīmāṃsakas, the common sense realists, raise specific objections to the Grammarian view on the grounds that it is not borne by experience. We have separate awarenesses of words and universals. While we may not perceive something as a cow prior to acquiring the word ‘cow,’ we are surely aware of cowness before we acquire the linguistic expression, just as we are aware of and can discriminate shades of red even before we acquire the names of some of those shades. A non-conceptual awareness of the object is implied by the subsequent occurrence of a conceptual awareness with determinate content. Kumārila also points to other phenomena which indicate that the awareness of the meaning of a word (the object) is independent and distinct from the word itself. Furthermore, awareness of the meaning and that of the word are usually different kinds of representations; there is no possibility of confusing or conflating these. Kumārila brings to attention linguistic phenomena that reinforce the point that words and meanings must be distinct representations, e.g., homonymy, synonymy, categorizing and recognizing grammatical parts of speech, etc. The ability to distinguish and discriminate types is perhaps enhanced by knowledge of language and concepts, but is not completely dependent on it. Those who are not trained in music can certainly hear the difference between distinct notes, even though they are unable to identify them by name. Vātsyāyana also appeals to the ordinary experience of people who are conversant with words. Ordinarily, words are apprehended as names of objects. The knowledge of the word-object association comes after the perceptual knowledge derived through sense-object contact. Such contact results in a perceptual awareness which, in turn, provides the occasion for recalling the appropriate word, if indeed the appropriate word exists in the experiencer's linguistic repertoire. Perceptual knowledge is antecedent to verbal knowledge and cannot owe its existence to words. Vācaspati Miśra specifically objects to Bhartṛhari's claim that infants and adults who lack a language perceive objects by memory impressions of their names from previous births. Objects are vividly and clearly given to us in perception, but the memory-impressions of previous births are at best vague and indistinct. Vācaspati Miśra asks, “How can such a vague and unclear thing be identified with a clear and distinct perception?” (Nyāyavārttikatātparyaṭīkā, p. 127). His other argument against Bhartṛhari is the obvious point that words do not necessarily refer to their objects, for example words in quotation marks do not refer to objects, only to themselves. Moreover, if the word and its denotation were identical, a blind man would grasp red or redness when he grasps the word ‘red’ and a deaf person would grasp the word ‘red’ when he grasps a red thing (Nyāyavārttikatātparyaṭīkā, p. 129).

The Naiyāyikas also have a general response to nominalists—Buddhists as well as Grammarians. They posit monadic universals that correspond to natural and metaphysical kinds and one dyadic universal, viz. inherence. The main nominalist objection is that once we accept real universals in our ontology we risk overpopulating the world with entities corresponding to every expression that designates a property. For example, if we accept horsehood and cowhood as universals, we also need to accept universalhood as another universal. The Naiyāyikas propose that not every expression which designates a property generates an objective universal (jāti); some property-expressions correspond to subjectively constructed categories (upādhi), which though useful for analysis, are not ontologically real. Uddyotakara argues that to correspond to a real universal a general term must meet two conditions: (i) a general term should be based on a ground, which accounts for the common awareness of a number of different objects, that makes the application of the term possible, and (ii) that ground should be a simple (non-compound), unitary property or entity that cannot be analyzed or explained away otherwise (Commentary on Nyāya-sūtra, 2.2.65). Universalhood is a bogus universal; it violates the second condition. There is no simple basis or ground for universalhood as opposed to universals such as cowhood and horsehood; the ground of being one-in-many can be analyzed in terms of inherence. The same applies to universals like ‘barefooted’, ‘cook’, ‘reader’ etc.; the basis for their application is presence of compound features such as bare feet, etc. However, this stratagem forces the Naiyāyikas to admit that many general terms designate bogus universals and, consequently, they start succumbing to the nominalist pressure. Matilal (1986, p. 420–421) notes that there is another way in which it happens to Navya-Nyāya: A real universal must partake of the nature of ‘one-in-many’. The Navya-Naiyāyika, Udayana (c. 10th century CE), lists a third necessary condition for disqualifying a property from being regarded as a real universal. Under this condition, an abstract property that belongs only to one individual is also a bogus universal even though it is simple and unanalyzable; skyness in the sky is bogus because it is only a nominal attribute. However, since both cowhood and skyness are simple properties, they are grasped as such in perception without further qualification. In this sense, Naiyāyikas maintain that some real universals are directly perceptible. When we see a cow, we do not necessarily see ‘it’ as a ‘cow’, the cow and the cowness are not given as separate entities in our awareness, rather they appear fused. This leads to the peculiar Nyāya view that real universals and basic properties are grasped in our awareness as ‘epistemic firsts’ or ultimates (Matilal, 1986, p.421). Gaṅgeśa calls such perception, in which universals are grasped as such, non-conceptual (nirvikalpaka) perception.

3.5 The Advaita Vedānta: a compromise on Hindu realism

The Advaita Vedānta theory compromises on the realism of earlier classical Hindu philosophy. Their early view on perception is akin to the Buddhists, although arrived at from a different perspective. Maṇḍana Miśra says:

Perception is first, without mental construction, and has for its object the bare thing. The constructive cognitions which follow it plunge into particulars. (Brahma-Siddhi, 71.1-2)

He draws a distinction between perceptual cognition and constructive cognition, but is careful to use vikalpa-buddhi, rather than savikalpaka pratyakṣa, for the latter cognition. For him perception is always non-conceptual (nirvikalpaka) perception and it is of a universal, indeed of the highest universal, Being (sat). According to early Vedāntins, the real is bereft of all character since its nature is non-differentiated consciousness or Brahman. Therefore, perceptual cognition, which presents the real, must be non-conceptual or indeterminate for it is the knowledge of the existence of a thing without any qualifications or predications. Maṇḍana Miśra also denies the thesis that non-conceptual (nirvikalpaka) perception is non-verbal. This surprising claim is clearly owed to Bhartṛhari's influence, as is evidenced by the example used by Maṇḍana Miśra in the argument. Confronted by an opponent with the claim that verbal knowledge involves duality and relation, and therefore must involve concepts, Maṇḍana Miśra replies that verbal knowledge is not necessarily relational: a baby's non-verbal knowledge of its mother's breast, grasps it merely as ‘this’ (of course we do not assume that the baby articulates the word ‘this’; the word, as in Bhartṛhari's account, has a more subtle form in the baby's mind) and, therefore, the highest knowledge of the Ultimate reality (Brahman) in which there is no duality, no relations, no concepts, may still be verbal.

Neo Advaita-Vedāntins, however, accept a distinction between non-conceptual (nirvikalpaka) perception and conceptual (nirvikalpaka) perceptions from empirical or practical (vyāvahārika) standpoint; from ultimate (paramārthika) standpoint such distinction is untenable. A brief description of conceptual (viṣayagata, Advaita-Vedānta term for savikalpaka) perception will help put in perspective Applebaum's (1982) reconstruction of their notion of non-conceptual (nirvikalpaka) perception later. Determinate perception is the result of the activity of mind (manas) or antaḥkaraṇa (literally translated as ‘inner vehicle’)—the terms are frequently used interchangeably. Advaitins maintain that the mind (antaḥkaraṇa) ‘goes out’ through the respective sense organ (the eye, say) and pervades the object of attention. As a result of this contact, the object presents itself as data to the receptive mind (antaḥkaraṇa) which, in turn, transforms into mental state (vṛtti) (Bilimoria, 1980, p.38). As soon as the data are presented to inner faculty, there is an identification of consciousness associated with the mental state (antaḥkaraṇa-vṛtti) with the consciousness associated with the object. To say that vṛtti and data are identified is to say that the form of the mental state, if all goes well, corresponds one-to-one with the form of the object; the mental state is a reflection of the object of perception, and as such is non-different from the object. Thus results a determinate judgment (vṛttijñāna) of the form “this is a jar”. Furthermore, according to them, we do not perceive our mental states; we directly perceive the objects themselves. Bilimora explains,

The vṛtti in the form of the object impresses itself as it were in the mode of the subject itself, and thereby comes to be apprehended, but as a predicate—and not as the pure subject-content which is the “I-notion”—in the subject's apperception”. (Bilimoria, 1980, p.41)

The initial mental state subsides and the subject becomes directly aware of the object itself; the cognition is self-evident to the subject, just like the cognition of pleasure and pain. In this reflective stage, the mind (antaḥkaraṇa) integrates the mental contents corresponding to the object with familiar or recognized percepts. Determinate perception of the totality of the object occurs with the completion of the assimilative process.

David Applebaum (1982) notes that Bilimoria's discussion of the Advaitin's notion of perception focuses on the necessary conditions or criteria for valid or veridical perceptions. According to him, this approach while justified in the light of perception's inclusion among the means of knowledge (pramāṇa-s) is mistaken because it only focuses on sensation as a species of mental state (vṛtti). For the Advaitin, sensation is not a mode exhausted by the judgmental content of a mental state (vṛtti), it has epistemic value independently of its role in judgmental perception. Applebaum quotes from the Upanisadic texts to support this view:

Manas is for men a means of bondage or liberation … of bondage if it clings to objects of perception (visayasangi), and of liberation if not directed towards these objects (nirviṣayam). (Applebaum, 1982, p.203)

Non-conceptual perception furnishes us with knowledge of pure existence (sanmātra) rather than with protodata to construct imagined particulars. Therefore, it is not simply a prior stage of conceptual perception and so also not necessarily a mental state produced in cooperation with the object. Applebaum (1982, p.204) suggests that non-conceptual perception in this sense focuses attention on sensing, in which consciousness turns its attention inwards to the activity of the sense-organs resulting in deepening and broadening their proprioceptive content. Proprioception, he claims, points the way to the soul or self (ātman); mind (antaḥkaraṇa) returns to its presentational activity, its function of monitoring and unfolding the sensory manifold to create conditions for the emergence of self (ātman), which according to the Advaitin, is identical with the Ultimate reality (Brahman). In non-conceptual (nirvikalpaka) perception, consciousness is returned to itself and opens up the possibility of manifesting or seeing the Seer (ātman) or knowing the Ultimate reality (Brahman).

4. Constructing Concepts or Knowing Universals?

The problem of universals, as we have seen, is at the epicentre of the debate between Hindu philosophers and their Buddhist opponents. The doctrine of exclusion (apoha) is the Buddhist attempt to account for the relation between concepts and sensory content. The doctrine of apoha basically claims that the term "cow" does not refer to the universal "cowness" or "cowhood" because there is no such general entity; rather, the term refers to every individual that is not a non-cow. In a recent paper Tillemans (2011) draws a useful distinction between two versions of the apoha doctrine: the top-down approach and the bottom-up approach. The former is presented by Diṅnāga who is also credited with introducing the doctrine of apoha. According to the top-down version, the negation operator in the exclusion, the apoha somehow manages pick out real particulars in the world while avoiding any commitment to universals. Apoha, in this sense functions like a sense or meaning, a not-non X expressed by the word X, which enables us to pick out real particulars while at the same time avoiding a commitment to real universals in virtue of the special features of double negation. The latter is presented by Dharmakīrti who uses the causal approach to link language and the world. According to this version of the doctrine, apoha provides a way to bridge the gap between sensory perception of particulars and expressions of belief and judgement in thought and language. The top-down version of the apoha doctrine was subjected to various criticisms from the Hindu realists, especially by Kumārila who criticised the doctrine on grounds of circularity. The thought is that in order to understand the exclusion class of non-cows, we have to first have an idea that some particulars are cows. In other words, one must be able to refer to cows before one can refer to non-cows. The bottom-up approach developed by Dharmakīrti was basically a response to this circularity worry. His version of the apoha doctrine is developed as a strategy to bridge the gap between non-conceptual perceptual content and conceptual content. Dreyfus (2011) develops Dharmakīrti's naturalized account of concept formation by elucidating the mediating role of representations that link reality to conceptuality. Representations, in this sense, stand for agreed-upon fictional commonalties and are projected on to discrete individuals (Dreyfus, 2011, 216).

The top-down approach is promising but there is a concern that a bottom-up account might not succeed in offering a completely reductive story about concepts. In response to this concern, Ganeri (2011) develops a hybrid account that combines the resources of the top-down and bottom-up approaches. The idea is that we work up from basic sentience and down from the language of reference and predication to meet at the middle-ground of feature-placing in the formation of proto-concepts (Ganeri, 2011, 244). These proto-concepts show that sense experience can normatively constrain belief and judgement, though it does not give us a full-blown reductive account of concepts in non-conceptual terms.

The doctrine of apoha and Ganeri's hybrid version may well be ingenious, but it is a far cry from what would satisfy the Hindu realist. According to Nyāya-Vaiśeṣika, universals exist in this very world of ours. We do not need to construct concepts from sensory content, rather universals are part and parcel of this sensory content. Chadha (2014, 289) explains that according to Nyāya, for a universal to exist all that is required is that it be exemplified; in a Quinean twist – to be is to be exemplified. There is no further requirement that it exist independently as an abstract entity or in Plato’s heaven; universals are given directly in perception insofar as their loci are perceived.

It is useful to think of a universal in this sense as a non-particular individual (Chakrabarti, 1995). Examples abound: Dusky is what many particulars are, though they may be spatiotemporally separated by many miles and years; rainy is what several days of the year can be at the same time in different places and at different times in the same place. If we are not thinking of universals as abstract entities in Platonic heaven or in the mind, but as individuals out there in the world, it is easier to grasp the idea that they can be perceived. The Nyāya equation of universals and properties might tempt one to think that Nyāya conceives of universals as natural properties in David Lewis’ sense of the term (Lewis, 1983), but such is not the case. Nyāya universals are as robust as Armstrong’s universals: they capture facts of resemblance and the causal powers of things. Naiyāyikas will happily endorse Armstrong’s ‘One over Many’ argument as the main reason for including universals in their ontology (Armstrong, 1978). Udayana puts the point thus: “Causality is regulated by universals, so is effect-hood. It is a natural universal if there is no obstruction [in establishing it]; it is a conditional [nominal] universal when we have to establish it through effort [construction?]” (Kiraṇāvālī, in Praśastapāda 1971, p. 23).

Although Gautama mentions universals in the Nyāyasūtras as the meaning of general terms,there is no explanation in these original sūtras as to how they might be known. Praśastapāda was the first to argue that universals are sensorily given. He argues that universals, when they inhere in perceptible loci (e.g., ‘cowness’ in an individual cow), are perceived by the same sense organs that also perceive those loci (Padārthadharmasaṃgraha, 99). This thesis is explicated in detail by Jayanta Bhaṭṭa in Nyāyamañjarī where he argues against the Buddhist nominalists as well as the holistic monist pan-linguist Bhartṛhari and his followers. Jayanta makes an allusion to the view that universals are given in indeterminate perception, a view later developed in detail by Gaṅgeśa in Tattvacintāmaṇi (the chapter on “Perception,” the section on “Indeterminate Perception”). Most of Jayanta's arguments against the Buddhist nominalist are discussed in detail in Chakrabarti (2006), however, he does not discuss the issue about universals being given in indeterminate perception. This is, as we have mentioned in the above sections, because Chakrabarti is sceptical about the coherence of the notion of indeterminate perception. Chadha (2014) argues that Gaṅgeśa makes a unique contribution to this debate in proposing the idea that universals or qualifiers are given as objects in indeterminate perception. He spells out his argument in terms of qualifiers rather than real universals, because the logical and epistemological role of a real universal is the same as that of a simple nominal property. Gaṅgeśa is concerned with basic, unanalyzable properties that can be grasped as such in our awareness. Basic properties in this sense are simple; they can be grasped without further qualification. They are, according to Nyāya, the ‘epistemic firsts’ comparable to non-conceptual perception in Buddhist epistemology. Gaṅgeśa’s argument is presented by Bhattacharya (1993, pp. 10-11) using a specific form of inference (parārthānumāna) developed in Nyāya for convincing others. It has a five-proposition structure:

  1. Proposition: The determinate perception of the form ‘a cow’ (or ‘that’s a cow’) is produced by the cognition of the qualifier.
  2. Reason: Because this is a qualificative cognition.
  3. Pervasion with an example: Every qualificative cognition is produced by a prior cognition of the qualifier, for example, inference.
  4. Application: The perception of the form ‘a cow’ is a qualificative cognition.
  5. Conclusion: Hence, it is produced by the cognition of the qualifier.

The weight of the argument rests on the third sentence. Gaṅgeśa supports it offering various examples of qualificative cognition, namely inference, recognition, analogy, verbal testimony, and so on. The point is that unless some awareness of dung is present in a person, (s)he cannot infer that there is dung on the hill on the basis of seeing some animals grazing on the hill. Universals like fireness and dungness are given directly in indeterminate perception. Gaṅgeśa’s argument maintains a causal uniformity among pramāna-generated cognitions of an entity as qualified (Phillips and Tatacharya 2004, p. 398). However, there is a problem: if anything that is known through a qualifier requires a prior cognition of the qualifier, there will be a regress of cognitions. Gaṅgeśa’s answer is that an indeterminate perception blocks the threat of such a regress, because the qualifier is then grasped directly rather than through another qualifier. In other words, the object is perceived through the property, but the property itself is perceived directly rather than through another property. The indeterminate perception, which precedes the determinate perception of an object through a mode, that is, as possessing a certain property, is not itself a perception through a mode. Simply put, we need to grasp the universal cowness in order to have an awareness of a particular as qualified by cowness. Chadha (2014) argues that Gaṅgeśa’s argument thus shows that the postulate of indeterminate perception of universals is a necessary requirement for realism.

5. Perceptual Illusion

The skeptics challenge strikes at the claim made by the Naiyāyikas that perception should be non-erroneous (avyabhichāri) and well-ascertained or free from doubt (vyavasāyātmaka). They ask: how do we distinguish between veridical perceptions and the non-veridical ones? In case of a perceptual doubt, say, seeing something at a distance which looks like a pole or an old tree-trunk, we are uncertain which it is but are a priori sure it cannot be both. In case of perceptual illusion, I see a snake but I misperceive as there is only a rope in front of me. Illusoriness of the experience (seeing a snake) is exposed with reference to another veridical experience (seeing a rope), but again, we are a priori sure that both cannot be true together. Then, the Buddhist skeptic, Vasubandhu, raises the ante with the question: could they not both be false simultaneously? The skeptical argument is premised on a denial of the realist thesis that experiences refer to a mind-independent reality. Vasubandhu's argument for idealism appears right at the beginning of Vimśatikā, when he states:

This [the external world] is consciousness only, because there is appearance of non-existent things, just as a person with cataracts sees non-existent hairs, moons et cetera. (Feldman, 2005, p. 529).

Vasubandhu offers many other examples of dreams, delusions, hallucinations, etc., where we are aware of non-existent objects that are products of our imagination and not objects external to the mind. If it is possible for awareness to create its own object and then grasp it (as in a dream) then, Vasubandhu argues, everything that we seem to be aware of could be a making of awareness.

The standard reply to this view appeals to the intuition that illusory experience is parasitic on veridical experience. The Naiyāyika, Vātsyāyana explains that an erroneous cognition depends on a principal cognition as its basis. “This is a man” for a tree-trunk, which is not a man, has for its basis a principal cognition of a man. If a man has never been perceived in the past, an erroneous cognition of a man, in what is not a man, can never be produced (Nyāya-Sūtra-Bhāṣya, 4.2.35). A similar argument is put forth by the Advaita-Vedanta founder Śankara. He challenges Vasubandhu's view on the ground that it is incoherent; when the Buddhists say “that which is the content of an internal awareness appears as though external,” they are

assuming the existence of an external thing even while they deny it … For they use the phrase ‘as though’ … because they become aware of a cognition appearing externally … For nobody speaks thus: Viṣnumitra appears like the son of a barren woman. (Brahma-Sūtra-Bhāṣya, 2.2.28)

Feldman (2005, p. 534) argues that this does not suffice to defeat Vasubandhu's idealism. The illusory experience of x, no doubt requires a memory impression which can be produced by a previous cognition, but there is no further requirement that the previous experience be veridical, because such impressions can be produced by illusory experiences. Feldman uses the case of someone who has only experienced snakes in dreams. He can mistake a rope for a snake, because the previous dream experience provides the necessary memory impression. Feldman's argument ignores the gravity of the concern raised by Vātsyāyana and Śankara, however. They reject Vasubandhu's argument on the grounds that we cannot imagine (dream, hallucinate, etc) an absolutely unreal thing, like a barren woman's son. The Nyāya theory of imagination, working in the background here, says that to imagine something is to superimpose or attribute properties belonging to one kind of thing to a thing of different kind, provided that there is some resemblance between the two kinds of objects (Uddyotakara's Nyāya-Sūtra-Bhāṣya, 3.1.1). For example, to imagine a centaur is to attribute a property belonging to the human-kind to a thing of the horse-kind. There is some general resemblance between the two kinds: both are animals and have legs. However, an ‘absolutely unreal’ thing can have no properties, and hence a fortiori no properties in common with an existing thing. They, therefore, cannot be an object of imagination.

Uddyotakara presents an even stronger argument against the skeptics. In his Nyāya-Vārttika he turns Vasubandhu's own argument against him. Uddyotakara asks: how do we know that the object of a dream experience is non-existent? Vasubandhu accepts that the dreamer does not know that he is dreaming; the knowledge that the object is non-existent occurs only when he awakens and no longer apprehends the object. If non-apprehension of an object in the waking state is required to support the claim that the objects of dream experience do not really exist out there, then apprehension in the waking state must be an indicator of their existence, otherwise there would be no contrast between what is apprehended and what is not (Nyāya-Vārttika, 4.2.33). If there is no such contrast, then Vasubandhu's argument fails because there is no support for the claim that objects of dream experiences do not exist in the external world. And, if there is such a contrast between apprehension and non-apprehension, then at least some external objects must exist. Clearly, Vasubandhu's argument for thesis of universal delusion (or idealism) does not succeed completely, nor are the realists totally defeated.

We close this entry on the note that Sūtra-s were primarily composed in the seven centuries from 5th BCE to 2nd CE and, thereafter, for the next millennium and more, the philosophical work was carried forward by Sūtra commentators (tikākār-s) from respective schools. This latter period saw these epistemological debates rage among scholars from these schools. Note also that there is no consensus on the dates given here; most Western scholars accept these, while Indian schools place them further back in antiquity.


Texts in English translation

  • Aksapada Gautama, Nyāya-Sūtra, with Vatsyayana's Nyayabhasya, Uddyotakara's Nyayavartikka, and Udayana'a Parisuddhi, A. Thakur (ed. and trans.), vol. 1, Mithila, 1967.
  • Bhartr̥hari, Vākyapadīya, Abhyankar K.V. and Limaye V.P. (eds.), Poona University, 1965.
  • Gaṅgeśa, Tattvacintāmaṇi, Epistemology Of Perception: Gaṅgeśa'sTattvacintāmaṇi, Jewel Of Reflection On The Truth (About Epistemology): The Perception Chapter (Pratyakṣa-khaṇḍa), Transliterated Text, Translation, And Philosophical Commentary, by Stephen H. Phillips and N.S. Ramanuja Tatacharya. Treasury of the Indic Sciences. New York: American Institute of Buddhist Studies, 2004.
  • Jayanta Bhatta Nyayamanjari: The Buddhist Refutation of jati. A Critical Edition (trans.) Kei Kataoka in The Memoirs of Institute for Advanced Studies on Asia, 160: 636(1)–594(43), 2011.
  • Uddyotakara, Nyaya-Vartika, in The Nyāya-Sūtras of Gauṭama: With the Nyāya-sūtra-Bhāṣya of Vātsyāyana and the Nyaya-Vartika of Uddyotakara, Gangānāṭha Jhā (trans.), Delhi: Motilal Banarsidass, 1984.
  • Uddyotakara, Nyāya-Sūtra-Bhāṣya, Translations from the introductory commentary on Nyāya-Sūtra-Bhāṣya, Arindam Chakrabarti (trans.), published as an appendix to A. Chakrabarti, “The Nyāya Proofs for the Existence of the Soul”, Journal of Indian Philosophy, 10: 211–238, (1982).
  • Vācaspati Miśra, Nyāyavārttikatātparyaṭīkā, Anantlal Thaur (ed.), Indian Council of Philosophical Research, 1996.
  • Vasubandhu, Viṃśatikā-Vṛtti, Triṃśatika, and Tri-Svabhāva-Nirdeśa, Thomas Kochumuttom (trans.), in A Buddhist Doctrine of Experience: A New Translation and Interpretation of the Works of Vasubandhu the Yogācārin, Delhi: Motilal Banarsidass, 1982.
  • Kumarila Bhatta, The ‘Determination of Perception’ Chapter of Slokavarttika, A Hindu Critique of Buddhist Epistemology: The ‘Determination of Perception’ Chapter of Kumarila Bhatta's Slokavarttika commentary by Taber, J. (trans.), Routledge Curzon Hindu Studies Series, New York: Routledge Curzon, 2005.

General works

  • Armstrong, D. M., 1978, ,Universals and Scientific Realism (Volumes I and II), Cambridge: Cambridge University Press.
  • Appelbaum, D., 1982, “A Note on Pratyakṣa in Advaita Vedānta”, Philosophy East and West 32:2, pp. 201–205.
  • Bhatt, Govardhan P., 1989, The Basic Ways of Knowing, Delhi: Motilal Banarsidass.
  • Bhattacharyya, Sibajiban, 1987, Gangesa's Theory of Indeterminate Perception Part 2: Containing the text of Gangesa's Nirvikalpakavada with an English translation and explanatory notes. Indian Council of Philosophical Research, New Delhi.
  • Bilimoria, P., 1980, “Perception (Pratyakṣa) in Advaita Vedānta”, Philosophy East and West, 30(1): 35–44.
  • Chadha, M., 2014, “On Knowing Universals: The Nyāya Way”, Philosophy East and West, 64(3): 287-303.
  • –––, 2001, “Perceptual Cognition: A Nyāya-Kantian Approach”, Philosophy East and West, 51(2): 197–209
  • –––, 2004, “Perceiving Particulars-as-Such Is Incoherent: A Reply to Mark Siderits”, Philosophy East and West, 54(3): 382–389
  • –––, 2006, “Yet Another Attempt to Salvage Pristine Perceptions!”, Philosophy East and West, 56(2): 333–342
  • Chakrabarti, A., 2000, “Against Immaculate Perception: Seven Reasons for Eliminating Nirvikalpaka Perceptions from Nyāya”, Philosophy East and West, 50(1): 1–8.
  • –––, 2006, “On Perceiving Properties”, in P.F. Strawson, and A. Chakrabarti (eds.), Universals, Concepts and Qualities: New Essays on the Meaning of Predicates, Aldershot: Ashgate, pp. 309-319.
  • –––, 2001, “Reply to Stephen Phillips”, Philosophy East and West, 51(1): 114–115.
  • –––, 2004, “Seeing Without Recognizing? More on Denuding Perceptual Content”, Philosophy East and West, 54(3): 365–367
  • –––, 1995, “Non-Particular Individuals”, in P. K. Sen and R. R. Verma (eds.), The Philosophy of P. F. Strawson, New Delhi: Indian Council of Philosophical Research, pp. 124–144.
  • Chakrabarti K., 1975, “The Nyāya-Vaiśeṣika theory of universals”, Journal of Indian Philosophy, 3: 363–382.
  • Coseru, C., 2012, Perceiving Reality: Consciousness, Intentionality, and Cognition in Buddhist Philosophy, New York: Oxford University Press.
  • Dreyfus, G. B. J., 2011, “Apoha as a Naturalized account of Concept Formation”, in M. Siderits, T. Tillemans, and A. Chakrabarti (eds.), Apoha: Buddhist Nominalism and Human Cognition, New York: Columbia University Press, pp. 207-228.
  • –––, 1997, Recognizing reality: Dharmakīrti's philosophy and its Tibetan interpretations, New York: State University of New York Press.
  • Feldman, J., 2005, “Vasubandhu's Illusion Argument and the Parasitism of Illusion upon Veridical Experience”, Philosophy East and West, 55(4): 529–541.
  • Ganeri, J., 2011, “Apoha, Feature Placing and Sensory Content”, in M. Siderits, T. Tillemans, and A. Chakrabarti (eds.), Apoha: Buddhist Nominalism and Human Cognition, New York: Columbia University Press, pp. 228-46.
  • Gupta, B., Dharmarajadhvarindra, and Anantakrishna Sastri, N. S., 1991, Perceiving in Advaita Vedanta: Ppistemological Analysis and Interpretation, London: Associated University Presses.
  • Kellner, B. and Taber, J., 2014, “Studies in Yogācāra-Vijñānavāda idealism I: The interpretation of Vasubandhu's Viṃśikā”, Asiatische Studien – Études Asiatiques, 68(3): 709-756. doi:10.1515/asia-2014-0060
  • Lewis, D., 1983, “New Work for a Theory of Universals”, Australasian Journal of Philosophy, 61: 343–77.
  • Lusthaus, D., 2002, Buddhist Phenomenology: A Philosophical Investigation of Yogacara Buddhism and the Ch'eng Wei-shih Lun (Curzon Critical Studies in Buddhism Series), London: Routledge.
  • Matilal, B. K., 1986, Perception: An Essay on Classical Indian Theories of Knowledge, Oxford: Clarendon Press.
  • Mohanty, J.N., 2000, Classical Indian Philosophy, Lanham, MD: Rowman and Littlefield.
  • Mondal, P. K., 1982, “Some aspects of perception in old Nyaya”, Journal of Indian Philosophy, 10(4): 357–376.
  • Phillips, S. H., 2001, “There's Nothing Wrong with Raw Perception: A Response to Chakrabarti's Attack on Nyāya's ‘Nirvikalpaka Pratyakṣa’”, Philosophy East and West, 51(1): 104–113
  • –––, 2004, “Perceiving Particulars Blindly: Remarks on a Nyāya-Buddhist Controversy”, Philosophy East and West, 54(3): 389–403
  • Siderits, M., 2004, “Perceiving Particulars: A Buddhist Defense”, Philosophy East and West, 54(3): 367–382
  • Thrasher, A. W., 1993, The Advaita Vedanta of Brahma-Siddhi, Delhi: Motilal Banarsidas.
  • Wezler, A. and Motegi, S., 1998, (eds.) Yuktidipika: The Most Significant Commentary on the Samkhyakarika, Volume 1 (Alt und Neu-Indische Studien, No. 41), Stuttgart: Franz Steiner Verlag.


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