This handbook is a voluminous collection of articles on a wide range of topics related to perception, which is, in the editor’s (p .1) words, “the ultimate source of knowledge about contingent facts.” Just how voluminous is this collection?  The 900+ page tome clocks in at four and one-half pounds and contains forty-five articles by fifty-five contributors.  So it occupies a fair bit of shelf-space.  It weighs in heavily–and well–on the metaphysics and science of perception, but is unfortunately significantly lighter when it comes to the epistemology of perception.  The inclusion of just a few more articles with an epistemic focus would have brought the volume close to being fully comprehensive.

The primary role a volume of this type should serve is to be a sophisticated introduction to a vast swath of the rapidly developing research on topics related to perception.  On this score, it delivers in spades.  A primary editorial aim looks to be to bring scientific discoveries to bear upon thinking about perception and related issues.  In that respect, the volume succeeds admirably, containing, for example, a rich selection of references to the scientific literature.  That said, at times, the volume can read more like a scientific or medical text than anything else.  And while the philosophical upshot of many of the mentioned scientific discoveries is not always obvious, readers will be rewarded by having, at their fingertips, a robust collection of scientific deliverances which do bear upon the nature perception.

Given the impossibility of thoroughly reviewing even a handful of the articles which appear in a tome of this length and breadth, and given how tedious a review consisting of single-paragraph summaries of forty-five articles would be, I will organize my review topically according to the seven major divisions the editor has opted for.  My primary purpose here will be to highlight interesting articles and point out interesting lacunas.

For those who want a summary conclusion, this volume definitely deserves space on the shelf of any student who is beginning to undertake a serious study of perception.  Intermediate students will find that the volume serves as a stellar source of references to many of the most important works in the extant literature and also points towards numerous rabbit holes which can, and should, be chased down.  Given the broad scope of the included material, advanced students will be able to treat the volume as a useful reference which covers various portions of the literature they may be less familiar with.

Division I:  Historical Background

This division sets the historical context from which the current burgeoning field of philosophy of mind has sprung.  This first division contains four articles which together trace the development of thought concerning perception from the Early Greeks (Victor Caston, “Perception in Ancient Greek Philosophy”) to the Medievals (Dominik Perler, “Perception in Medieval Philosophy”) through the Early Moderns (Alison Simmons, “Perception in Early Modern Philosophy”) and finally on to the 19th and 20th Century (Gary Hatfield, “Perception in Philosophy and Psychology in the 19th and Early 20th Centuries”). 

These chapters are not fully comprehensive (e.g., notably absent in the discussion of medieval theories of perception is any mention of John Duns Scotus or Henry of Ghent), but nor should they aspire to full comprehensiveness.  They serve their purpose as introductions incredibly well, and though some might maintain that talk of “sensible species” is neither necessary nor helpful in a volume which is designed to serve as an introduction to contemporary research, I would disagree.  The editor deserves praise for including this historical material, and contemporary research on historical figures is, of course, a relevant part of this rapidly developing field.

Finally, the section on historical context is fleshed out with three more chapters concerned with, respectively, sense data (Paul Snowdon, “Sense Data”), skepticism (Baron Reed, “Skepticism and Perception”), and phenomenology (Charles Siewert, “Phenomenological Approaches”).  These articles are generally well-informed. It is also noteworthy that Franz Brentano has not been overlooked (by Siewert) in a volume with a significant scientific bent.  And while I generally enjoyed Snowdon’s discussion of sense data, which is historically informed, Snowdon’s criticisms of sense-datum theorists struck me as falling a bit flat if one has in mind somewhat more contemporary approaches to sense data (on which, e.g., sense data aren’t conceived of as possibly bent immaterial entities).  Still, for the purposes of stage-setting, one could hardly ask for a better historical introduction.

Division II: Contemporary Philosophical Approaches

This division appears to be a sort of catch-all category which focuses on presenting fairly abstract (some might say “esoteric”) technical philosophical scholarship.  One might wonder, for example, why this division comes before the third (“The Senses”) which treats (among other things) of vision, audition, and touch.  After all, it would seem natural, after providing historical context, to kick off a handbook on perception with a discussion of the five primary sensory modalities.  Here I could only speculate as to the editor’s decision.  That would be a pointless exercise, and so rather than doing that, I’ll try to explain why I’d have made the same choice.

In this division one is introduced to some fundamental philosophical positions concerning issues related to perception all of which are receiving widespread contemporary attention and over which there is still widespread disagreement.  One can think of these fundamental positions as frameworks (a.k.a. “mini-worldviews”) the adoption of which can have a significant influence on one’s thinking about perception.  Are hallucinatory experiences categorically different in kind from the experiences one has in veridical perception (Heather Logue, “Disjunctivism”), and if so, does this difference have epistemic consequences?   Do experiences, perhaps like pictures, represent something as being the case (Bence Nanay, “Perceptual Representation / Perceptual Content”)?  If so, what do they represent as being the case?  And if experiences represent some things as being the case, must one possess concepts in order for them to do so, or is what they represent as being the case independent of the concepts one possesses (Wayne Wright, “Nonconceptual Content”)?

The answers one gives to these questions, to which the reader is here introduced, may well shape how one conceives of the relationship between perception and knowledge.  It is, I believe, worthwhile to introduce the reader to these questions and their various possible answers before moving on to a more concrete discussion of the senses and their supposed deliverances.

All that said, I have concerns about how well this section manages to achieve all the goals it should.   One reason for this concern turns on the general problem that there is no generally accepted manner of using terminology.   For example, we are informed (p. 199) that a hallucination of a banana is a “perceptual experience as of a yellow, crescent shaped thing.”  This is somewhat odd, and likely to be confusing to the reader, since when one hallucinates a banana, one quite arguably doesn’t perceive anything at all (and certainly doesn’t, say, perceive a banana, since there is no such banana to be perceived). (The idea that hallucination involves perception of sense-data enjoys very little support even though the it is not entirely uncommon to find philosophers who hold that perception involves sense-data in some way.  Seeing a banana is to perceive a banana, but if such perceiving somehow involves sense-data, one needn’t think that a sense-datum, rather than a banana, is perceived.)  I take it that it would be better, here, to speak of a sensory experience as of (or a sensation as of) a banana.  Perhaps some readers will be able to determine that this is what is occurring and that perception is not–or need not be–at issue here, though I have my doubts.  After all, this is the Oxford Handbook of the Philosophy of Perception, and one might well be led to believe that hallucination is a form of perception–a claim that is widely granted to be false by contemporary philosophers who work in this area.

Another potential form of terminological confusion arises within this division’s discussion of perceptual content where a form of representationalism is floated.  And while one form of “representationalism” is here taken up, the term “representationalism” is ambiguous in the literature.  In this division, the term is used to pick out theories upon which experiential states somehow represent something or, alternatively, have content.  Another common use of the term, however, picks out a theory (more commonly termed intentionalism in the contemporary literature) according to which the representational content of an experience supervenes upon the phenomenology of the experience.  This form of representationalism receives almost no mention in this volume–though it is marginally broached (pp. 648-651) by Malika Auvray and Ophelia Deroy in “How Do Synaesthetes Experience the World?”  This is a fairly glaring omission.

Furthermore, many will probably find themselves comfortable distinguishing between an experience being a representation and its having representational content.  Perhaps analogously, pictures are representations which do not have representational content?  And there is a distinction between an experience having intentionality (being about something) and the content of that experience.  One could maintain that a perceptual experience of Eiffel Tower is about the Eiffel Tower but nevertheless lacks representational content.  Finally, we can, I presume, distinguish between perceptual content and representational content in various ways. Perhaps the perceptual contents of perceptual experiences are objects and properties while the representational contents of those experiences are propositions? 

These distinctions do not get clearly drawn (though Wayne Wright’s “Nonconceptual Content” draws an elegant and entirely appropriate yet far too often overlooked distinction between content nonconceptualism and state nonconceptualism which will help with making them) and they are critically important issues in the debates concerning the content of experiences.  One would expect an article in a handbook of this sort to take some of them up.  But the extent to which they are taken up is not clear–especially so given that the primary article devoted to it (Bence Nanay, “Perceptual Representation / Perceptual Content”) concerns “perceptual content” which may or may not be equivalent to “representational content”.  And while readers are instructed that perceptual contents may come in many different forms (e.g., it is floated without explanation that perhaps they are “Russellian gappy” or “Fregean gappy”), this will not be of much benefit to what I take to be a significant portion of this handbook’s audience, though granted, readers are referred to other literature (which they will need to consult if they hope to make sense of this). 

My point is not that the contributions made in the section “Contemporary Philosophical Approaches” are not valuable.  They are, and immensely so.  For example, Heather Logue’s chapter “Disjunctivism” is one of the clearest and most even-handed introductions to the topic I am aware of.  Rather, my sense is that several of these contributions are directed at seriously advanced students.  These contributions are by no means readily accessible to “anyone who has an intellectual interest in issues concerning perception” as the cover jacket claims.  They are, perhaps, more suited for providing advanced graduate students with a rough and general but nevertheless incomplete sense of the topics along with extensive directions for further research (which research will require having institutional access.)  Those who aren’t already familiar with extensive swaths of the literature are going to have to work hard to determine what is going on.  Given the foundational nature of the subject matter and the extensive debates surrounding these topics, that is to some extent to be expected, but I would have preferred if this division had leaned further in the direction of somewhat more elementary, stage-setting contributions.

Division III:  The Senses

The third main division, “The Senses,” begins with independent articles on the visual, auditory and tactile faculties.  The gustatory and olfactory sense modalities are discussed together in a separate chapter: “The Chemical Senses”.  This division is rounded out with two further chapters: “The Bodily Senses” and Jesse J. Prinz’s excellent “Unconscious Perception”.  Taken together, this division covers all the five standard sensory modalities and more. 

In J. Brendan Richie and Peter Carruthers “The Bodily Senses” we are told (p. 354) that

Interoception is most familiar to philosophers through the conscious bodily sensations it         produces.  Itches, thermal sensations, sensations of orgasm, heart-beat, thirst, indigestion, shortness of breath, and any form of pain, along with aspects of moods, emotions and affect more generally, are all forms of interoceptive experience.

Here, perhaps, we might expect to find our discussion of inner perception (introspection). Is that not also a potentially important source of knowledge about contingent facts?  Yet in this chapter this reader was left somewhat cold.  To be clear, I don’t mean to suggest that the authors ought to have taken up a discussion of introspection, but given that this was the only included chapter in which it might be thought to get taken up, it didn’t seem to be.  For the most part (with some minor exceptions), this volume focuses primarily upon outer perception broadly construed so as to include perception of one’s bodily states.  Nevertheless, this omission is interesting.

A notable aspect of this division is that, when it comes to the better-known or better scientifically investigated outer senses, we get less philosophy and more science.  When it comes to the less well-known or less scientifically investigated outer senses, we get more philosophy and less science.  Thus David Hilbert’s chapter “Vision” contains extensive passages such as the following:

The other two cone-types (M-cones and L-cones) have closely spaced peak sensitivities near the middle of the spectrum.  By sampling the retinal image with three        spectrally different photoreceptor types, the visual system acquires information about the spectral power distribution of the light falling on it, and not just its intensity. (p. 261)

What the philosophical upshot of this is supposed to be is unclear, not the least because it’s unclear what the “visual system” is or what “information” that system actually acquires.  Here is another example:

From the retina, the main pathway supporting vision proceeds to the primary visual cortex (V1) by way of the dorsal lateral geniculate nucleus of the thalamus (LGN).  (p. 264)

While the science here is interesting, I’m not certain what the philosophical upshot is supposed to be.

What to make of this?  I’m unsure.  There is no question that good philosophical thinking about perception often depends, in large part, upon familiarity with the science which lies behind perception.  In some cases, the science clearly matters when it comes to philosophical theorizing.  In other cases, I am inclined to think that it doesn’t matter so much.  So at times, I am led to suspect that philosophically uninteresting science is trotted out at the expense of engaging in serious philosophy.  That said, every chapt