Descartes, Malebranche, and the Crisis of Perception by Walter Ott (review)

This is a short book on a small topic with big ramifications. I call it a small topic because Descartes's account of perception occupies only a corner of his overall philosophical project, which is dominated by his concern to provide a solid metaphysical and epistemological grounding for his science. At the same time, Ott's discussion of sense perception in Descartes comes part and parcel with an account of the theory of ideas in Descartes and later Cartesians (especially Malebranche, but also La Forge, Desgabets, Régis, and Arnauld), a theory of how to read the Meditations (especially relative to his other writings), and an interpretation of Descartes's mind-body dualism, including the similarities and differences between human beings and non-human animals.

The "crisis in perception" that Ott has in mind is generated by the demise of the Aristotelian account of our perceptual and intellectual engagement with the world, whereby perceived qualities such as color and sound are real properties of things and the "common sensibles" are perceived by perceiving the "proper sensibles." By the seventeenth century, this explanation, along with the "Baconian synthesis," whereby sensible species literally travel from external bodies to our sense organs and cognitive faculties, was replaced by the mechanical philosophy, which required its own account of how bodies with geometrical properties are perceived both as individual items in our environment and how it is that we perceive them with the properties they appear to have. As Ott puts it, "If bodies have no sensible qualities, how is it that we come to see them otherwise?" (218).

Ott offers a developmental reading of Descartes's approaches to the challenge. He distinguishes four stages in Descartes's thought on sense perception. In the "early" stage (which according to Ott starts with the Treatise on Man and then leap-frogs over the Discourse on Method and the Dioptric of the mid-1630s—which belong to the second stage—to include the Meditations), Descartes has the mind "turning towards," "looking at," or "inspecting" images in the brain, especially on the pineal glad. These material images represent external bodies by resembling them; and the mind can read these images as well as "summon the appropriate sensation" to perceive those bodies with their features. At this stage, the mechanisms of perception are roughly the same for inattentive humans and non-human animals.

In stage two, present in the Dioptric, the "mind looking at the brain" model gives way to a more causal account, with brain motions causing sensations according to a relationship instituted by nature. In stage three (Sixth Replies) and stage four (Principles of Philosophy and Passions of the Soul), Descartes's account undergoes further modifications, with sensations and other ideas eventually generated in the mind on the occasion of the appropriate brain events, a relationship instituted by God.

One problem persists throughout these stages, namely, what is the relationship between the sensible qualities caused/occasioned in the mind by the motions in the brain and the common sensibles that, on Ott's reading, are grasped by the mind attending to the brain (pineal) images? Why do we see individuated bodies not only with size and shape, but also as colored? How do qualities get localized onto particular geometric bodies?

Ott admits that his account is "contentious." For example, sensations, he insists, are not ideas for Descartes. Moreover, if Descartes's views on sense perception are really as much in flux as he describes, if his views truly moved through these distinct stages, one wants to know what moved Descartes to change his mind. Here Ott does not have much to say. But this is precisely what he needs to discuss to defend the dialectic that he finds across Descartes's texts. He only briefly addresses the "why" question: He simply says that Descartes "loses faith" in the account in which the mind attends to the brain image. But then why would Descartes, after toying with another account in the Dioptric, resuscitate...