Robert Howton

I attribute to Aristotle a theory of sensible qualities that straddles the modern debate between reductive physicalist and primitivist theories of color. On the interpretation I defend, Aristotle identifies sensible qualities with the physical properties of sensibly qualified bodies in virtue of which they move and affect perceivers and sense media. Nevertheless, I argue, Aristotle thinks that the essential nature of these qualities is revealed in ordinary sense experience. From a modern perspective, the resulting picture of sensible qualities as simultaneously causes and manifest features of sense experience appears naive. But as I hope to show, it is in fact the product of an explanatorily sophisticated scientific theory, one which Aristotle finds necessary to meet the complex demands that, for him, make sensible qualities an ontological problem.

Sense experience, naïvely conceived, is a way of knowing perceptible properties: the colors, sounds, smells, flavors, and textures in our perceptual environment. So conceived, ordinary experience presents the perceiver with the essential nature of a property like Sky Blue or Middle C, such that how the property appears in experience is identical to how it essentially is. In antiquity, as today, it was controversial whether sense experience could meet the conditions for knowledge implicit in this naïve conception. Aristotle was a partisan in this debate, but his position is poorly understood. This dissertation examines how Aristotle’s perceptual psychology responds to ancient challenges to the naïve conception, and so articulates his defense of perceptual knowledge. Aristotle’s defense relies on an ontology of “perceptual qualities"—a core class of perceptible properties—according to which those qualities, despite having a perceiver-independent essence rooted in the physics of causation and affection, nevertheless can be present in experience as they essentially are. Chapter 1 defends this realist and objectivist reading against competing interpretations, which overlook a crucial distinction between perceptual qualities and perceptual objects. Chapter 2 presents Aristotle’s ontology as a physicalism that uncharacteristically allows for perceptual qualities to appear in experience as they essentially are. This ontology informs Aristotle’s account of the psychological conditions under which perceivers actually are presented with the essence of perceptual qualities. The locus of this account is an obscure passage where Aristotle purports to show that the senses “discriminate” perceptual qualities because the senses are “mean states” (An. 2.11, 424a5–7). Chapter 3 develops a comprehensive interpretation of the sensory mean state, which Chapter 4 uses to elucidate Aristotle’s argument for sensory discrimination. Sensory discrimination turns out to be a process in which the essence of a perceptual quality comes to be present in the affection it produces in a perceiver. For Aristotle, this shows that sense perception meets a condition for knowledge that his predecessors, including Plato, thought it could not meet. For in his view, but not in theirs, sense experience shares in both the truth and the essence of the qualities it perceives.

The soul is an explanatory principle of Aristotle’s natural science, accounting both for the fact that living things are alive as well as for the diverse natural attributes that belong to them by virtue of being alive. I argue that the explanatory role of the soul in Aristotle’s natural science must be understood in light of his view, stated in a controversial passage from Parts of Animals (645b14–20), that the soul of a living thing is a “complex activity” of its organic body. This paper explores the role of this “complex activity” model of soul in Aristotle’s study of soul in De Anima. I argue, first, that the model has its origins in De Anima II.4, where Aristotle argues that living things do all they do by nature for the sake of a single, teleologically primary end. I argue further that Aristotle uses this model to account for the psychological attributes naturally present in living things, including their capacities for vital activities like nutrition, reproduction, and perception, and that this is the task to which Aristotle devotes the obscure final chapters of De Anima III.