[The reviewer offers his apologies for the late appearance of this review.]
An “object” for the purposes of this book is an integrated whole that we encounter as such, that is, as a whole rather than as a mere assemblage of sense data. When a perceiving subject turns his eyes toward some object of this kind, say, a tree, he perceives immediately colors and various intensities of light and shadow. But in addition to these immediate sense data he also sees a tree, that is, he is cognitively aware of the integrated whole that is present in addition to the many and widely varying data of light, shadow, color, and even shape. This last property—shape—is a perceptual object not restricted to vision alone but is one of the “common sensibles”, a sensible property that can be the object of more than one proper sense. How this happens has long been a staple topic in the philosophy of perception, and in this excellent new book Anna Marmodoro defends a strikingly original interpretation of how Aristotle understood this process to work. Her study will be of interest not only to historians of philosophy but also to anyone interested in the philosophy of perception and the ontology of dispositional properties.
The book begins with a long and detailed discussion of Aristotle’s theory of potentiality. This first chapter, “The Metaphysical Foundations of Perception,” is extremely interesting not only because of the light it sheds on Aristotle’s theory but also because of Marmodoro’s detailed discussion and use of contemporary “power ontology” as a hermeneutic for understanding Aristotle’s own language of dispositional properties. On Marmodoro’s account, Aristotle regards efficient causation as a function of the interaction of active and passive relative pairs, for example, “capable of heating” and “capable of being heated”. The metaphysics of change is thus reducible to properties that interact with each other in terms of active and passive modes: the change from not-hot to hot is reducible to the co-instantiation of the active power of heating and the passive power of being-heated. In every case of change there will be two such properties, each property being ontologically independent of the other yet neither occurring in the absence of the other.
Chapters 2 and 3 present Marmodoro’s main interpretation of Aristotle’s theory of perception, beginning in Chapter 2 (“Aristotle’s Causal Powers Theory of Perception”) with an application of the results of Chapter 1 to Aristotle’s account of perception as the reception by the sense organs of the form of the proper sensibles and extending to Chapter 3 (“Aristotle’s Subtle Perceptual Realism”) in which Marmodoro explains Aristotle’s realism about perception in terms of the capacities of objects in the world to interact with perceiving subjects. A color just is a capacity to be seen, and sight just is a capacity to see (specifically, to see color and light). Aristotle is thus a realist about the proper objects of perception because the capacities to be seen, to be heard, to be felt, etc. are not merely subjective qualia but are in fact real features of the external world that have an independent existence whether or not they are being experienced by some perceiving subject. However, on Marmodoro’s account the distinction between first and second actuality marks the intimate connection that nevertheless exists between a proper sensible and the perceiving subject. Sounding, she says (p. 131), is an object’s capacity to produce an instance of hearing in a perceiving subject—this is the second actuality of the capacity that is sounding. But a sound can also exist—as a first actuality—when it is not actually heard. So it turns out that the tree falling in the forest when nobody is there to hear it does make a sound: in the form of a first actualization of the capacity to produce an instance of hearing when somebody is there to hear it.
The remainder of the book (Chapters 4 through 7) applies this interpretation of Aristotle’s overall theory of perception to the specific problem of complex perceptual content, that is, content that is mixed in terms of its perceptual origins but that is perceived as an integrated whole. Such an account is necessary because it seems obvious, from the point of view of the phenomenology of our experience, that we do not perceive the world as “arrays of disjoint perceptibles” (p. 156) but as consisting of discrete objects. Aristotle’s standard account of the faculties of soul, however, requires that each faculty respond to a specific proper object that is qualitatively distinct from the proper objects of every other faculty—vision to light and color, hearing to sounds, etc. This specialization of faculties is not limited to the perceptual faculties, but applies to the rational faculties as well— epistēmē taking the necessary truths of logical relations as its proper object, for example, phronēsis taking the contingent truths of practical reasoning for its proper object, etc. In order to account for our experience of the world as consisting of unified objects, then, Aristotle must posit some further activity of soul to account for our ability to integrate the distinct perceptual data of the special senses. Like other commentators, Marmodoro sees Aristotle giving a special role in this regard to the perceptual faculty as a whole, that is, to perception understood as the full suite of special sensory modalities. Seen in this way, perception as such is more than the mere sum of its modal parts, but constitutes a “common sense” that is in some sense distinct from the five special senses and that performs certain integrative functions. These functions involve not only the so-called “common sensibles” that can be detected by more than one special sense (shape, motion, size, etc.) but also, and more importantly, the delivery of integrated epistemic content that is not available to any individual special sense in the case of common sensibles (p. 174). For Marmodoro, this means that “the agent perceives a unified object by perceiving the unified common sensibles that qualify it” (p. 179).
Aristotle was an empiricist, holding that we abstract universals from particulars over a period of multiple perceptual encounters, and these universals form the basis for the conceptual content that is the proper object of nous. This process is described in Posterior Analytics II.19 and in Metaphysics I.1. Marmodoro discusses neither of these passages, but it would have been extremely interesting to hear what she has to say about them in light of her view that Aristotle attributes a kind of cognition to the common sense (pp. 161-2). She contrasts Aristotle’s view with that of Plato, who had argued, in the Theaetetus, that the senses deliver their data to a higher faculty of judgment without making any cognitive assessment of those data on their own. Aristotle’s view, she says, was motivated by a desire “to explain the complex cognitive abilities of animals without appealing to the capacities of the intellective part of the soul, because this is unique to humans and not common to all animals” (p. 162).
This may be right, but it isn’t clear what sort of “complex cognitive abilities” non-human animals are supposed to have. In Posterior Analytics II.19, 99b35-100a2 Aristotle claims that for animals without a faculty of memory there is no knowledge beyond perceiving ( ouk esti toutois gnōsis exō tou aisthanesthai). It does not follow from this that Aristotle thinks that perceiving constitutes a kind of knowledge for animals without memory, nor should we assume that non-human animals that do have memory are capable of the sort of cognition that Aristotle goes on to describe in the human case. It is quite clearly epistēmē and tekhnē that do the cognitive work (100a9) in humans; memory and experience ( empeiria) play less well-defined roles in the process. So what, precisely, is it for perception to have cognitive content? The bulk of Marmodoro’s project aims at explaining the integrative nature of the common sense, but she says little about what she means for the common sense to have a cognitive capacity beyond describing it as integrative in some way. In contrasting the common sense with the special senses, she notes that the special senses have “only a partial epistemic hold on each of the common sensibles” (p. 174). Though this is the only occurrence of the word “epistemic” in the book, it is suggestive. The context seems to imply that (a) the special senses have a full “epistemic hold” on their respective proper objects and (b) the common sense has a full “epistemic hold” on the common sensibles. Though Marmodoro does not define “epistemic hold” it is difficult to avoid the assumption that it has something to do with epistemic content, and if we are to believe that perception—either as such or in the form of the special modalities—has epistemic content then the project of explaining the cognitive power of perception seems to have grown exponentially. Aristotle begins his analysis of cognition in Posterior Analytics II.19 by noting that perception is a connate discriminatory capacity ( dunamin sumphuton kritikēn 99b35) shared by all animals, and Marmodoro does an excellent job of explaining in what sense perception is “discriminatory” as well as in what sense it is a capacity. But Aristotle’s account of cognition concludes by claiming that we see a tree not merely as a discrete individual object bearing perceptible properties, but as a tree, as an instantiation of a natural kind, and so far commentators have been unable to explain how Aristotle thinks we get from the merely discriminatory stage to the fully cognitive stage at which we achieve understanding of the conceptual content associated with the underlying universal.
Since Aristotle himself fails to explain this we can hardly fault his commentators for doing the same, and yet Marmodoro has done exemplary work in bringing us closer to understanding the details of Aristotle’s theory of perception even if she has left us hungry for more. Her work will be necessary reading for anyone interested in the philosophy of perception, and by putting it into the context of contemporary power metaphysics she has made Aristotle’s theory of more than antiquarian interest.