The Object View of Perception

Abstract

We perceive a world of mind-independent macroscopic material objects such as stones, tables, trees, and animals. Our experience is the joint upshot of the way these things are and our route through them, along with the various relevant circumstances of perception; and it depends on the normal operation of our perceptual systems. How should we characterise our perceptual experience so as to respect its basis and explain its role in grounding empirical thought and knowledge? I offered an answer to this question in Perception and its objects (Brewer 2011). Here I aim to clarify some of my central arguments and to develop and defend the position further in the light of subsequent critical discussion.

We perceive a world of mind-independent macroscopic material objects such as stones, tables, trees, and animals. Our experience is the joint upshot of the way these things are and our route through them, along with the various relevant circumstances of perception; and it depends on the normal operation of our perceptual systems. Such perceptual experience is a rich and varied conscious condition that makes a significant contribution to our capacity for thought and knowledge of the world. How should we characterise this experience so as to respect its basis and explain its role in grounding empirical thought and knowledge? I offered an answer to this question in Perception and Its Objects (Brewer 2011). Here I aim to clarify some of my central arguments and to develop and defend the position further in the light of subsequent critical discussion.¹

I begin in Sect. 1 with a brief overview of the project: to state and motivate the Object View (OV). In Sect. 2 I consider various objections to my arguments against its orthodox alternative, the Content View (CV). Section 3 turns to a defense of (OV) itself against objection.

1 The Object View

There are no doubt other approaches to the taxonomy of theories of perception, but I regard the most basic question in the area as this. What is the most fundamental nature of our perceptual relation with the material world around us; e.g. of my seeing a laptop before me now? I understand this as a request for an account of what it is to perceive that is both explanatorily adequate and metaphysically acceptable. That is, the proposed account should explain and unify the characteristic features of perception, such as its phenomenology and its role in making thought and knowledge of the world possible, in a way that meets the general criteria for evaluating metaphysical theories: what is required for perception must be consistent with our best overall account of what there is.

I see three broad categories of answer to the basic question. First, perception consists most fundamentally in a relation of acquaintance with various mind-dependent sensations. A subsidiary question is then whether these are themselves elements of a mind-dependent material world or whether they are, normally at least, appropriately causally dependent upon sufficiently resembling mind-independent material objects as to constitute our indirect perception of such things. Second, perception consists most fundamentally in our representation of things as being thus and so in the mind-independent world around us. Crucial subsidiary questions then concern the experiential mode of representation, its content, and also the relations between these and phenomenological character. Third, perception consists most fundamentally in a relation of acquaintance directly with the constituents of the mind-independent world. Perception and Its Objects offers arguments against the first and second of these, along with an extended development and defence of a specific version of the third.

This Object View (OV), takes the basic worldly relata of the acquaintance relation to be mind-independent material objects. Acquaintance is construed as an unanalysable conscious relation that we are enabled to stand in with such things by the normal functioning of our brains and perceptual systems. Distinct experiences may have identical objects of acquaintance, though. For example, experiences of a round red disc head on, from a wide angle, or edge on, in bright or dim lighting conditions, and so on. So a simple appeal to the object of acquaintance is inadequate to explain the nature of our various experiences of the same thing. We are acquainted with the objects around us from a given spatiotemporal point of view and in certain specific circumstances of perception, and (OV) treats these factors as a third relatum of the relation of acquaintance that holds between perceivers and the objects of perception. Focusing throughout on vision, our experiences are cases of being visually acquainted with a particular mind-independent material object from a given spatiotemporal point of view and in certain specific circumstances.

Now the objects that we see look various ways to us. The core of the (OV) account of looks is that an object of acquaintance, o, thinly looks F iff o has, from the point of view and in the circumstances of perception in question, appropriate visually relevant similarities with paradigm exemplars of F. These are similarities by the lights of the various processes enabling and subserving visual acquaintance: similarities in such things as the way in which light is reflected and transmitted from the objects in question and the way in which stimuli are handled by the visual system given its evolutionary history and our shared training during development. Furthermore, some, but not all, of these thin looks will be salient to us in any particular case, for example, as we switch between the duck and rabbit looks of the duck-rabbit figure. I say that an object, o, thickly looks F iff o thinly looks F and the subject registers its visually relevant similarities with paradigm exemplars of F. The paradigm case of registration as I understand it involves the active deployment of the concept of an F, but (OV) also recognizes a variety of significantly less demanding modes of registration, including those involved in systematic behavioural responses, such as simple sorting, and those involved in the noticing of various organisational, orientational, or other gestalt phenomena.

Illusory experiences, in which o looks F although it is not, are cases of acquaintance with an object from a point of view or in circumstances in which it has visually relevant similarities with paradigm Fs although it is not itself an instance of F. These similarities may, but need not, in turn be registered.

Hallucinations, on the other hand, are cases of experiences without looks-grounding objects of acquaintance, whose correct theoretical characterization is rather that they are not distinguishable by introspection alone from cases of acquaintance with a given qualitative scene from a specific point of view. Some experiences pre-theoretically classified as illusions may involve a conjunction of successful acquaintance with some degree of hallucination in this sense caused by the relevant worldly objects. Furthermore, since acquaintance depends on the satisfaction of significant and highly complex physiological enabling conditions, there will also be abnormal experiences that are correctly to be characterized in terms of partial failures in acquaintance: cases of degraded acquaintance. These cases of total and partial failure of acquaintance are essentially derivative of the success that grounds veridical and illusory, thin and thick, looks, according to (OV). Assimilating all such cases is incompatible with giving an adequate explanation of the fundamental role of perception in grounding thought and knowledge about the mind-independent world. To reiterate a slogan of the book, the ways that things look to a person in perception are in the first instance the looks of the very mind-independent things that she is consciously acquainted with from the point of view and in the circumstances in question.²

I develop a number of these ideas in Sect. 3 below in response to specific objections to the explanatory adequacy of (OV).

2 Against (CV)

Objections have been given to my three main arguments against the Content View, (CV), according to which perception is instead most fundamentally a matter of experientially entertaining contents concerning the way things are in the mind-independent world. I consider each of these in turn.

2.1 Falsity

According to (CV), paradigm cases of illusion are visual experiences that represent an external object, o, as F although it is not F. This basic idea of a false representational content concerning o involves no limit on the nature and extent of the error involved in predicating F of o.^{3 , 4} Yet the objects of our visual illusions are presented in experience—we actually see them—and there are significant limits on the nature and extent of the errors compatible with genuine experiential presentation. For example, if it looks to me as though there is a black cube in front of me, then this is not a case of seeing the white disc that is actually there, even if this is in some way responsible for the cube appearance.⁵ My first objection is that (CV) cannot resolve this tension. For it offers no explanation of these limits on error compatible with seeing.

Proponents of (CV) may reply that it is no requirement on the theory to provide such an explanation.⁶ On their view, our perceptual relation with the world around us is a matter of experientially entertaining certain contents. Seeing o involves experientially entertaining a content, p, concerning o, provided that any errors in p are within certain limits.⁷ But it is not the responsibility of a theory of perception to state what those limits are, or why those are the limits governing perceptual presentation, or even where one might go to find out the answers to these questions. Indeed, it may be objected further that (OV) is in the end in exactly the same position vis-à-vis explaining the limits on error compatible with seeing. I take these two points in turn.

An analogy may be helpful in seeking to justify this rejection of the explanatory requirement that I argue (CV) objectionably fails to meet.⁸ Consider Williamson’s response to the Gettier literature (1995, 2002). Williamson grants that it is no objection to the idea that belief is a necessary condition on knowledge that no explanation or conjunctive analysis can be given of which (true) beliefs are and which are not cases of knowledge. Similarly, my opponent claims that it is no objection to the idea that experientially entertaining a content concerning o is a necessary condition on seeing o that no explanation can be given of which contents concerning o are within the limits on error required for seeing o and which fall outside these limits.

This seems right to me, so far as it goes. But I take Williamson’s central claim to be that knowledge is basic: ‘knowledge first’, as he puts it (2002, p. v). Knowing that p is the most fundamental condition in the area, not to be explained in other terms, but rather capable itself of illuminating the involvement of more derivative cognitive conditions such as believing that p. This is what makes his acknowledgement of believing as a necessary condition on knowing consistent with the motivated rejection of any need for an account or explanation of any ‘additional’ conditions on knowing. And Williamson’s ‘knowledge first’ thesis is precisely analogous to my own (OV) reaction in the case of perception. Conscious acquaintance, actually seeing o, is the most fundamental condition in the area. Taking this as basic it is possible to explain the various ways that things look in perception. Taking the way things look, which may be either veridical or illusory, as basic, on the other hand, as (CV) does, it is impossible to work up from there to any adequate account of seeing the things in the world around us. Yet that is precisely what is required by the (CV) commitment to the idea that our perceptual relation with the world is most fundamentally a matter of experientially entertaining contents concerning the way things are in the mind-independent world.⁹ The analogy with Williamson harms rather than helps (CV).¹⁰

Furthermore, in response to the second point above, unlike (CV), (OV) does have an explanation of the limits on error in illusion compatible with seeing, although of course it starts with seeing itself and derives the limits on error rather than vice versa. Given acquaintance with o, there are limits on the ways o may look: it may look just those ways, F, such that o has, from the point of view of acquaintance and in the circumstances in question, visually relevant similarities with paradigm exemplars of F.¹¹

According to (CV), our perceptual relation with the material world is most fundamentally a matter of our experientially entertaining certain representational contents concerning the way things are in the mind-independent world. Its current challenge is to explain which errors in such contents concerning a particular material object o are compatible with actually seeing o. I cannot see how this is supposed satisfactorily to be met. According to (OV), on the other hand, our perceptual relation with the material world is most fundamentally a matter of our conscious acquaintance with the constituents of the mind-independent world around us. Its corresponding challenge is to explain which ways, both ways that o is and ways that o is not, o may look, given that we are acquainted with that very thing from a given spatiotemporal point of view and in certain specific circumstances. Unlike (CV), (OV) at least attempts to meet precisely this challenge. O thinly looks F iff o has, from the point of view and in the circumstances of perception in question, appropriate visually relevant similarities with paradigm exemplars of F. O thickly looks F iff o thinly looks F and the subject registers its visually relevant similarities with paradigm exemplars of F. Notice also that this account has the further advantage that it accommodates and explains the dependence of the errors compatible with seeing in any particular case upon the specific point of view and other circumstances of perception involved in that case of acquaintance with the relevant worldly object.

2.2 Generality

The most natural development of (CV) characterises the contents that we experientially entertain in perception purely generally in terms of the various predicates that are apparently instantiated by whatever it may be that we perceive, or fail to perceive, before us. Yet perceptual presentation is manifestly particular. Seeing is a conscious relation that we stand in to particular worldly objects. So (CV) faces the question of what determines the particularity of the perceptual relation. The objection from falsity considered above concerns the degree of correspondence, or ‘fit’, that must be involved between the predicates ascribed by the relevant content, p, and the actual condition of the object, o, seen. Whatever the required fit may be, the contents that we experientially entertain nevertheless fit indefinitely many numerically, and indeed qualitatively, distinct actual and possible material objects. The current problem is to specify what determines the unique particular such object that we actually see on any given occasion.

The obvious solution is to appeal to the causal explanation of our entertaining the content p on the occasion in question. O will be the object appropriately involved in that causal explanation. A first difficulty for this solution is to specify exactly what appropriate involvement is supposed to be. Many objects, perhaps even many within the required degree of fit, may be involved in some way in the causal explanation of our entertaining p on a given occasion. What mode of involvement uniquely identifies o as the object that we see? This is of course a very familiar problem that has generated a large literature.¹² It is absolutely genuine, though, and the complete lack of consensus in its solution may well lead one again directly to an analogue of Williamson’s ‘knowledge first’ response to the Gettier literature: seeing an object is basic, a matter of being consciously acquainted with o from a given point of view and in certain circumstances of perception, precisely as (OV) contends, rather than being any kind of composite of experientially entertaining a content, p, in some way concerning o, along with the satisfaction of further necessary and jointly sufficient conditions.¹³

Suppose for the sake of argument that this first difficulty may be overcome. My principal objection from generality remains. (CV) fails the requirement of explanatory adequacy on any satisfactory theory of perception in connection with the role of perceptual experience in explaining our capacity for reference to particular material objects in the world around us (see Campbell 2002a, b). Intuitively, in many cases at least, and perhaps in the most basic cases, this capacity for reference depends upon our conscious perception of the particular objects in question. The reason that I can refer determinately to that particular bottle of San Pellegrino on my desk, as opposed to any of the others that may be littered around my office, say, and that I genuinely understand which bottle it is that I am referring to, is that I see it right there in front of me. One may of course reject this intuitive explanatory role of perception in relation to reference. But it seems to me to be extremely robust and I assume it without further argument in what follows. The difficulty now for the current version of (CV) is that that particular bottle is supposed to be entirely extrinsic to the fundamental nature of my perceptual-experiential condition: selected simply by the additional causal conditions whatever exactly these may be. So it is quite mysterious how being in that perceptual condition is supposed to explain my capacity to refer, with understanding, to that very bottle as opposed to any other. It is effectively an additional assumption of this objection that the contribution to the subject’s understanding that is made by a conscious mental condition that he may be in is restricted to what is intrinsic to the fundamental nature of that very condition. I entirely accept that this is highly controversial. But I endorse the restriction and explicitly make the additional assumption here.¹⁴

Again, there may appear to be a straightforward solution: to claim that reference to the particular object that is seen is intrinsic to the content that characterises the fundamental nature of our perceptual experience according to (CV). The result is still explanatorily inadequate, though. For experientially entertaining the proposed content now simply presupposes what seeing o is supposed to explain, namely, our capacity for reference to that very object. The requirement is to give perceiving o an explanatory role in connection with our capacity for reference to o. Yet the revised (CV) account characterises perceiving o precisely in terms of reference to o: a matter of experientially entertaining a content that itself refers to o.¹⁵

So (CV) faces a dilemma. If reference to o is extrinsic to perceptual content, then perception is incapable of explaining our capacity for reference; if reference to o is intrinsic to perceptual content, then perception presupposes our capacity for reference and is therefore again incapable of explaining it. (OV) seizes upon the obvious structural solution. Perception is most fundamentally a matter of our acquaintance, from a given point of view and in specific circumstances, with the material objects in the world around us: a relation that is particular in its key worldly relatum, yet not a matter of entertaining any kind of perceptual representational content. Thus, it is at least intelligible how perceptual experience may play a genuinely explanatory role in connection with our capacity for reference, with understanding, to those very things.

2.3 Determinacy

My third objection to (CV) is rather a challenge to its proponents to give an adequate account of which contents specific perceptual experiences have, and why. Once again, a possible reply presents this as an unmotivated demand for some kind of analytic reduction of perceptual content to more basic facts about perceivers. Some theorists offer such,¹⁶ but others deny independently that it can or must be given.¹⁷ Perhaps, as Pautz puts it (2014, p. 6), “the non-intentional facts determine what contents a person experientially entertains, even though there is no finitely specifiable, general algorithm for going from the non-intentional facts to the facts about experiential content”. In that case, my challenge is no real threat to (CV): it can simply be swept aside.

This is not how I see the situation, although I grant that this is not clear from the discussion in my book. The challenge is rather that there are plausible features of the content-like aspects of perception that are quite unintelligible on the assumption that the perceptual system simply serves up specific experiential contents fully formed and without any explanatory dependence upon more basic experiential facts in particular cases. In contrast, I claim that (OV) does provide the required intelligible explanations.

The features that I have in mind are twofold. First, thin looks are massively varied and multiply nested. A splash of paint may simultaneously (thinly) look red, bright red, scarlet, shade r₂₇, … zig-zag, snake-like, the shape of a crotchet (quarter-note) rest, …, whereas (CV) proposes that the system serves up single colour and shape predicates in terms of which it is supposed determinately to be classified in experience. Second the far more specific thick looks that are registered by a perceiver acquainted with a given object on a particular occasion are systematically dependent upon her experience to date, her interests and projects at the time, and so on: upon which questions she is posing of the object of her perception on that occasion. Again, the (CV) idea that experience simply selects one answer is incompatible with the presence of a whole world to her in experience that she interrogates in these specifically directed ways. The rich completeness of the world itself and the particular answers to her specific concerns that she ascertains from it in directed perception are both part of the way things look to her. Yet (CV) compresses these two quite different levels of looks into a single layer of perceptual representational content. So I claim that content-determination really is a problem for (CV). Its flat and one-dimensional appeal to specific experientially entertained contents simply served up to the subject by the system lacks the richness, variety, and depth required to capture the manifold looks of the worldly objects that we perceive.¹⁸

It may be objected in return that the range and variety of thin looks entailed by (OV) constitutes a problem for the position rather than a challenge to its opponents.¹⁹ For this is effectively to embrace a kind of indeterminacy in the way things look in any particular case.²⁰ A white piece of chalk under red illumination, for example, thinly looks red and thinly looks white-in-red-light: its look bears both descriptions. Likewise, a red piece of chalk under normal white illumination thinly looks red and thinly looks white-in-red-light. The phenomenon is quite general, and may appear to stand in the way of appealing to the looks of things in explaining our detection of specific features of the worldly objects around us on the basis of perception, such as the redness, as opposed to whiteness (in red light), of a red piece of chalk. But that appearance would be misleading. For our registration of some, but not others, of the visually relevant similarities with various paradigms that the objects of our acquaintance actually have from the points of view and in the circumstances of our acquaintance with them constitutes our being struck by, or noticing, determinate such looks. Thus things thickly look specific ways to us in a sense that thereby contributes to our detection of their specific features. Furthermore, as noted in Sect. 1 above, the cognitive demands on the most basic forms of such registration may be really quite minimal. So determinate specificity in environmental detection is relatively straightforward to attain.²¹

3 Defence of (OV)

My own (OV) has also been subject to serious objection, both in principle and in connection with specific, largely non-ideal, experiential phenomena. I begin with two principled considerations (Sects. 3.1 and 3.2) and then turn to the specific cases (Sect. 3.3).

3.1 Opposition

3.1.1 (OV) and (CV)

Is (OV) really in opposition to all versions of (CV)?²² My simple answer is ‘yes’, as I define them. According to (OV), the most fundamental characterisation of our perceptual relation with the world is in terms of our acquaintance with mind-independent objects, whereas (CV) claims that this is in terms of our experientially entertaining various truth-evaluable contents. I take the most fundamental characterisation to be unique and these two candidates are distinct. So the views are incompatible. But the situation is in reality less straightforward.

First, as I have already stressed, (OV) entirely accepts that there are content-like characterisations of our perceptual conditions. Indeed, it offers detailed explanations of specific such thin and thick looks on the basis of the relata of conscious acquaintance on any particular occasion: the worldly objects of acquaintance and the point of view from which, and circumstances in which, the perceiver is acquainted with them. So, far from being inconsistent with the claim that perception always involves something content-like, (OV) goes to great lengths to develop a nuanced account of the thin and thick looks that accordingly capture its ‘content’. Various truths of the form ‘o looks F to S’ are its recognition of what (CV) elucidates in terms of S (visually) experientially entertaining the content that o is F. The point is that (OV) takes acquaintance as basic and explanatorily derives the wide variety of ways in which the objects that we are acquainted with may look, rather than taking the idea of experientially entertaining the content that p as fundamental and aiming to provide a complete theory of perception on that basis instead.

Second, there are versions of (CV) that propose object-dependent contents for perceptual experience. It is a necessary condition on entertaining such contents that the perceiver be suitably related to the worldly objects in question. So in this sense perception may be a relation to such things according to (CV) too. Nevertheless, provided that it adopts the attitude that perception is most fundamentally a matter of experientially entertaining such contents concerning the way things are in the mind-independent world, then this is precisely a variant of (CV), as I understand it, and it is therefore intended at least to be subject to the objections that I have just been rehearsing.

Third, there might also be a possible version of (CV) with purely Russellian perceptual contents composed of worldly objects and their perceptible property instances. As with the object-dependent view, it follows from entertaining such contents that one stands in a derived relation with particular worldly objects, but the property side of the perceptual condition is again taken as equally basic rather than being an intelligible consequence of the nature of the object of acquaintance, point of view, and circumstances, as on (OV). So, again, the problems of generality and content-determination remain. Furthermore, I take it that this variant of (CV) loses what is often regarded as its major advantage in offering an account of illusion and hallucination in terms of false perceptual contents. For in such cases there are simply not the objects and property instances to serve as constituents of an appropriate Russellian content. This may be an advantage by the lights of the (OV) objection from falsity to (CV), but, correlatively, a disadvantage by the normal lights of proponents of (CV) themselves. I myself also have reservations about the metaphysical standing of the proposed property instances. In any case, such a view is certainly not a ‘technical variant’ of (OV), as Brogaard suggests (2014). It is once again a variant of (CV) in opposition to (OV).

Fourth, and finally, returning to my initial characterisation of the two views, is there not room for a no-priority view intermediate between (CV) and (OV), on which acquaintance with particular worldly objects and experientially entertaining perceptual contents are independent and equally fundamental? In order to assess any specific such proposal it would be necessary to see the details. But I do have general concerns about the basic idea that shape my own division and evaluation of the available options. If the (OV) account of looks on the basis of acquaintance is even close to right, then the postulation of an independent and equally fundamental content characterisation of perception is unmotivated and unnecessary, and a no-priority view would in any case be subject at least to the content-determination problem outlined above. Furthermore, given their independence, what would be supposed to rule out potential conflict between the acquaintance and content bases of perception in any particular case?²³

3.1.2 (OV) and (IR)

I distinguished three categories of answer to the basic taxonomic question for theories of perception: what is the most fundamental nature of our perceptual relation with the material world around us? (CV) and (OV) constitute the second and third respectively. It has also been objected that (OV) is committed to something like an indirect realist version of the first, according to which perception consists most fundamentally in a relation of acquaintance with various mind-dependent sensations.²⁴ The idea is that the (OV) emphasis on the point of view of acquaintance in accounting for the way things look in perception effectively assimilates the position to one on which our perceptual relation with indirect external objects of perception is somehow the result of computations on more basic direct objects such as retinal images.

Of course I agree that retinal image size, say, depends on the distance from worldly object to the perceiver’s viewpoint. But there is no obvious reason to believe that every theory that gives the perceiver’s point of view a role in accounting for the way things look is committed to regarding such retinal images as the direct objects of perception in any sense. Computations on ‘retinal images’ are essential physiological enabling conditions on our visual acquaintance with worldly things, but this is conscious acquaintance with them—the worldly objects—and not with such retinal images that are not objects of perception at all. Furthermore, the way things look in perception, according to (OV), is to be understood in terms of the looks, from certain points of view and in certain circumstances, of those very worldly objects of acquaintance themselves, rather than being accounted for in terms of the nature of any mind-dependent supposed objects of acquaintance.

3.2 Indistinguishability

According to (OV), visual acquaintance is an unanalysable conscious relation between subjects, mind-independent worldly objects, and their spatiotemporal point of view and relevant circumstances, that we are enabled to stand in by the evolutionarily established integration of our perceptual systems with the relevant ways of the world. It provides the explanatory ground of the most basic ways that things look to us in perception. The explanations that (OV) provides of the way things look in perception on the basis of such acquaintance have the consequence that introspectively indistinguishable looks may be grounded in quite distinct relata of acquaintance. This is so not just in the case of acquaintance with perfect duplicates in identical viewing conditions, but also, as we have already seen, for example, between cases of acquaintance with a red wall in normal lighting conditions and with a white wall bathed in red light, or between cases of acquaintance with a round disc from an angle and with an elliptical disc head on, and so on. It is also a consequence of the view that looks which are indistinguishable from those grounded in some such way may on occasion be entirely ungrounded in any acquaintance: this is precisely characteristic of hallucination. So introspectively indistinguishable perceptual experiences may have quite different fundamental natures according to (OV). For their fundamental nature is characterised precisely in terms of the subject’s acquaintance, from a given point of view and in specific circumstances, with particular material objects in the world around him.

Many commentators find this consequence objectionable²⁵ for they simply assume that the only adequate explanation of introspective indistinguishability must cite an identity at the level of the fundamental philosophical characterisation of the experiences in question. (OV) explicitly rejects this principle, and I claim that the rejection is entirely compatible with the criterion of explanatory adequacy on theories of perception that I endorsed at the outset. For (OV) provides a perfectly adequate alternative explanation of introspective indistinguishability in such cases in spite of distinct fundamental experiential constitution, by appeal to the ‘visually relevant similarities’ account of looks and the ‘negative epistemic’ account of hallucination, both sketched above.²⁶

Perhaps this exchange illuminates an interesting distinction, or possibly a continuum, between philosophical approaches in the area. Top-down theorists begin with a conception of what conscious perception is for: it makes thought and knowledge about the world possible. Then they derive an account of what such perception must be, at least in its central cases, in order to do this. Bottom-up theorists begin with the most varied possible list of perceptual phenomena and an intuitive indistinguishability criterion of theoretical identities between them. Then they sculpt a theory that best follows the contours of that imposed taxonomy treating all cases as equal. My point here is that, if a top-down theory is capable of explaining, or at least accommodating, the more unusual phenomena assembled by those working from the bottom up, even whilst rejecting the identification of indistinguishable experiences, then those phenomena can be no ground for rejecting the top-down theory in question. Indeed, if its promise of making sense of what perception is for is met, then the top-down theory retains the upper hand. From this point of view, what is lacking in the bottom-up approach is any sensitivity to the distinction, amongst the whole range of weird and wonderful perceptual phenomena, between the normal or paradigm cases that sustain the wider philosophical role in connection with thought and knowledge, on the one hand, and those that are instead some kind of failure, or deviation from this norm. Indeed, treating all cases alike and adhering to the indistinguishability criterion of identity may be in tension with an adequate account of the normal case. In Sect. 3.3 below I consider the question of whether (OV) can accommodate certain of the phenomena in the evidence base of opposing bottom-up theories. I end the current section with a sketch of this direct threat to the bottom-up approach generally, that the flattening effect of its introspective indistinguishability criterion of experiential identity stands in the way of any adequate account of the explanatory role of the normal case in connection with thought and knowledge.²⁷

Suppose that we partition perceptual experiences purely by introspective indistinguishability. Very crudely, equivalence classes will contain all and only those experiences in which things look exactly the same to their subject. Thus, each will contain all and only those experiences in which it looks to the subject as though there are objects with such and such properties arranged thus and so in the world around him. The characteristic feature of the maximally bottom-up approach to philosophical theorizing about perception, as I intend it, is that their membership of such an equivalence class exhausts the fundamental nature of every experience in it. That is to say, the fundamental nature of each such experience is precisely that it is one in which it looks as though there are objects with such and such properties arranged thus and so in the world around the subject.²⁸

Now, on the assumption that we are working with every actual and possible perceptual experience of a subject like us in a world like ours, then a privileged subset of the experiences in any given equivalence class will be wholly veridical-perceptual: he actually sees that there are objects with such and such properties arranged thus and so in the world around him. Most will be partially veridical-perceptual in this way and partially illusory, in various proportions and combinations. An outlying subset will be wholly hallucinatory. All are absolutely identical in fundamental nature. Just as (CV) aims to tame hallucinations as experiences of the very same fundamental kind as certain genuine perceptions—these are all cases of experientially entertaining a content concerning the way things are in the world around the subject—this bottom-up approach has the consequence that the perfectly veridical perceptions and all the various illusions in any given equivalence class of experiences are all identical in fundamental nature with its outlying wholly hallucinatory experience. These are all mere perturbations of consciousness, as it were, in which things look thus and so, entirely ungrounded in their fundamental nature in the subject’s actual relations with the world out there.

It is true that all such experiences are introspectively indistinguishable from seeing various objects with such properties arranged thus and so in the world around him. But there is nothing more to the nature of this wholly veridical-perceptual condition than there is to a complete hallucination in which things merely look just that way. So any idea of perception itself as a relation between minded subjects and the world that they inhabit that makes the particular constituents of that world available for thought and is revelatory of their actual nature in a way that serves as a source knowledge is seriously strained. The crucial role of perception in grounding thought and knowledge is quite mysterious.

Contrast with this the (OV) understanding of perceptual experiences partitioned by introspective indistinguishability. These again fall into equivalence classes of experiences in all of which things look exactly the same to their subject. But, except for the outlying total hallucination, such looks are in every case grounded in her conscious acquaintance with various particular objects in the world around her from various points of view and in various circumstances of perception. This grounding constitutes the fundamental nature of the experiences in question and so serves intelligibly to explain the role of perception in making thought and knowledge of the world possible. Total hallucinations are limiting cases of experiences merely introspectively indistinguishable from such acquaintance, from actually seeing various objects with such and such properties arranged thus and so in the world around her.²⁹

Proponents of (CV) find this account of hallucination unsatisfactory. But one way to put the current objection to the bottom-up approach is that it produces theories of perception on which all perceptual experiences are brutely indistinguishable by introspection from certain perceptions: that is most fundamentally what they are. Furthermore, there is nothing more that can be said about the veridical perceptions themselves that supposedly support this entire experiential structure either: they are most fundamentally experiences that are simply indistinguishable by introspection from various hallucinations. So the whole account is in serious danger of coming crashing down.

3.3 Problem Cases

Can (OV) adequately accommodate the more peripheral and abnormal experiential phenomena that its opponents object are inconsistent with its acquaintance-based account of the way things look in perception? It will be evident in what follows that the distance between the accommodation and complete explanation of such phenomena may increase as such phenomena diverge from normal perception. But I take this to be inevitable and perfectly acceptable on the top-down approach that gives the normal case philosophical explanatory priority and construes more peripheral cases as a kind of failure or deviation from the norm. I have already sketched two resources available in the (OV) account of simple illusion and total hallucination, respectively: (i) the existence of visually relevant similarities between an object of acquaintance, from a given point of view and in specific circumstances, and paradigm exemplars of a kind of which it is not itself an instance; and (ii) the idea of experiences that are simply indistinguishable by introspection alone from cases of acquaintance with a given qualitative scene from a specific point of view in the absence of any grounding in acquaintance. I now consider two additional resources available in accommodating further phenomena that opponents object are a threat to the position: degraded acquaintance and hallucinatory projection.

3.3.1 Degraded Acquaintance

Conscious visual acquaintance is a relation between subjects, mind-independent worldly objects, and their spatiotemporal point of view and relevant circumstances, that we are enabled to stand in by the evolutionarily established and fine-tuned integration of our perceptual systems with the relevant ways of the world. Given such conscious acquaintance with an object, o, from a given point of view and in specific circumstances, then o thinly looks F iff o has, from that point of view and in those circumstances, appropriate visually relevant similarities with paradigm exemplars of F; o thickly looks F iff o thinly looks F and the subject registers its visually relevant similarities with paradigm exemplars of F. In cases in which there is some abnormality in, damage to, or interference with, the processes enabling acquaintance, or an extension beyond their normal domain of operation, then degraded acquaintance may result, in which only some of the more determinable (less determinate) thin looks of the objects of acquaintance are available and registered in thick looks. In general, the thin ways things look are given by all of its visually relevant similarities with relevant paradigms from the point of view and in the circumstances in question. Acquaintance with o from this point of view and in these circumstances brings these into consciousness for potential registration. Degrading reduces the thin looks available for registration in certain respects and on certain dimensions to merely determinable looks.

For example, blurred vision may in certain cases involve a failure of acuity in boundary determination. In such cases the object of acquaintance certainly has visually relevant similarities with objects of a range of different sizes and shapes. Thus it looks determinably boundaried within that range. For whatever reason, though, the subject’s acquaintance is degraded. So it does not look of any more determinate size and shape.

It has been objected to any view along these lines that it fails adequately to distinguish the perception of fuzzy objects from the blurred perception of sharp objects.³⁰ My reply is to claim that this distinction is precisely absent at the level of thin looks, but that it absolutely does shows up, phenomenologically, at the level of thick looks. Suppose, first, that I am acquainted with a fuzzy object, such as a cloud, perhaps, whose boundary is not precise. Its boundary is determinably within a certain spatial range, but not determinately located more precisely than that. It has, from my point of view and in the circumstances, appropriate visually relevant similarities with paradigm exemplars of something determinably boundaried thus—within such and such a spatial range. Indeed, it may well be just such an exemplar. Hence it thinly looks merely determinably boundaried within that range. Thinking about its spatial extent, I may register just those similarities and it therefore thickly looks, as it is, indeterminately boundaried. This I take to be a further genuine feature of the way things are for me phenomenologically.³¹ Second, suppose that I am peering at a sharp-edged white rock without my glasses. My acquaintance with it is therefore degraded, and, although it actually has appropriate visually relevant similarities with paradigm exemplars of a something determinately shaped and extended, only its more determinable looks are available to me. Once again it thinly looks merely determinably boundaried within a given range. I may mistakenly categorise it as actually indeterminately boundaried. In which case it thickly, and illusorily, looks fuzzy. On the other hand, I may rightly recognise the source of its thinly looking merely determinately boundaried as down to me, and correctly resolve the thin ambiguity that way, as it were. Again, this is a genuinely phenomenological matter, and to mark it we say that I see the rock blurrily. So (OV) captures the genuine phenomenological distinction with the perception of fuzzy objects in the context of its basic appeal to blurred vision as degraded acquaintance.³²

I take red-green colour-blindness, at least of certain kinds, to be a second example of degraded acquaintance. The way things look is again constituted by their highly determinable visually relevant similarities: the tomato looks coloured, of a certain brightness, and perhaps we might even say that it looks red-or-green. It may be difficult for normally sighted subjects to be any more specific because there is nothing more specific to say. Perhaps it looks greyish, as the red and green snooker balls look indistinguishably grey on black and white TV. Maybe this goes some way towards capturing the visually relevant similarities between them that characterize the determinable looks of both to red-green colour-blind subjects. In any case, such subjects’ visual systems are sensitive only to colour-like features shared by red and green things. So their acquaintance with them is degraded in such a way that they only have conscious access to their appropriately determinable looks.

(OV) may exploit this idea of degraded acquaintance and correspondingly determinable looks in accommodation of many more peripheral perceptual phenomena too. I take the above as illustrative for present purposes and turn now to hallucinatory projection.

3.3.2 Hallucinatory Projection

According to (OV), hallucinations are experiences whose fundamental nature is simply that they are indistinguishable by introspection alone from cases of acquaintance with a given qualitative scene from a specific point of view. These may be caused by neurophysiological intervention or narcotic ingestion. They may also be caused by external objects. For example, a hammer blow to the head may cause a hallucination of stars or the scent of certain paints may cause hallucinations of various, perhaps related, coloured lights. Visual stimuli may even cause systematically related visual hallucinations. For example, bright lights of certain colours may cause hallucinations of patches of light of related colours apparently located on a wall in front of the subject. (OV) accounts for after-images in just this way, as experiences introspectively indistinguishable from acquaintance with patches of light of the relevant colour on the surfaces before the subject. Notice that such hallucinations are conjoined with genuine perception of the surfaces themselves on which they appear. This is what I mean by the projection of hallucinations onto genuine objects of acquaintance, and such hallucinatory projection provides a rich resource for the accommodation of peripheral and abnormal perceptual phenomena within the (OV) framework.

Hermann’s Grid is a case in point. This is normally classified as an illusion: pale grey patches illusorily appear at the intersections of the white channels formed by a grid of closely spaced black squares. (OV) offers an alternative explanation of the phenomenon as a hallucinatory projection onto the stimulus grid, systematically caused by its closely packed black squares. We are acquainted with the grid of black squares itself, and this experience is conjoined with a systematic hallucination introspectively indistinguishable from acquaintance with light grey patches at the intersections of the white channels between these black squares that is projected onto it somewhat in the manner of an after-image.

I end the current section by considering a fascinating phenomenon whose accommodation plausibly involves the conjunction of degraded acquaintance and hallucinatory projection.³³ Philosophers working on visual perception are now quite familiar with type-1 blindsight, in which subjects have the ability to discriminate visual stimuli but report having no associated sensory consciousness: they regard their successful discrimination as pure guesswork.³⁴ In type-2 blindsight, on the other hand, patients are consciously aware of external objects, in some sense at least, and can determine some of their features; but the phenomenology of their experience does not correspond directly with any such features of the objects that they thereby detect.³⁵ That is to say, the ways things look, on the basis of which subjects are able to determine various features of the objects around them, are not simply the looks that those very objects actually have from the point of view in question and in the relevant circumstances. This is apparently in tension with the (OV) account of looks.

The strategy that I propose in response is to combine the resources of degraded acquaintance and hallucinatory projection. Suppose we take at face value the idea that type-2 blindsight patients are consciously aware of the objects around them. That is to say, according to (OV), they are visually acquainted with those very things. But, due to their neurological condition, their acquaintance is seriously degraded. So they only have conscious access to their highly determinable looks, such as their visually relevant similarities simply with something shaped and sized within quite an extensive range—moving, or pulsing, for example. Furthermore, their condition may also produce experiences of hallucinatory projection onto these objects of their acquaintance. And although these may be systematically correlated with certain of the features of the relevant worldly objects, as the colours of after-images are correlated with the colours of the bright lights that produce them, they are not directly revelatory of the ways those things actually are or look from the point of view in question. A full (OV) account of any individual case would have to combine these two elements as appropriate to its specific details. But I see no difficulty in principle with such a combination, and it certainly yields a rich variety of options and possibilities.

In any case, patients may exploit their prior knowledge of such a correlation between certain of the ways things look in perception and the ways that they are told they are in order to use their perceptual experience as a source of new knowledge of the way things are in the world around them on any particular occasion, rather as I may use the position of the needle on my speedometer as a source of knowledge about the speed that I am driving. They will also thereby recognise, as they do, the peculiarity of their predicament. For the looks on the basis of which they learn that there are objects with such and such properties in the world around them are not, in their case unlike in ours, straightforwardly the looks of those things from their point of view in the relevant circumstances. Some of them, at least, are instead instrumental hallucinatory indicators of what is out there before them.

4 Conclusion

I began by distinguishing three approaches to developing a philosophical theory of perception. I have said relatively little about the first of these, on which perception consists most fundamentally in a relation of acquaintance with various mind-dependent sensations, other than to register my conviction that it fails with respect to both explanatory adequacy and metaphysical acceptability. I have refined and extended my objections to the second, (CV), according to which perception consists most fundamentally in our representation of things as being thus and so in the mind-independent world around us. Finally, I have argued that my own (OV) implementation of the third approach, on which perception consists most fundamentally in a relation of conscious acquaintance with the constituents of the mind-independent world themselves meets the theoretical requirement of explanatory adequacy with respect to empirical thought and knowledge, and with respect to phenomenological variety, in a metaphysically acceptable and defensibly top-down way. I conclude that (OV) is a theory worthy of serious consideration.