[Readers] are invited to explore problematic or advanced features of Aristotle's theories by following the appropriate links.

• Aristotle's Psychological Writings
• Hylomorphism in General
• Hylomorphic Soul-body Relations
• Supplement: A Fundamental Problem about Hylomorphism
• Supplement: A Question about the Metaphysics of Souls
• Psychic Faculties
• Nutrition
• Perception
• Supplement: A Controversy Surrounding Aristotle's Theory of Perception
• Supplement: Imagination
• Mind
• Desire
• Bibliography
• Other Internet Resources
• Related Entries

Aristotle's Psychological Writings

Aristotle investigates psychological phenomena primarily in De Anima and a loosely related collection of short works called the Parva Naturalia, whose most noteworthy pieces are De Sensu and De Memoria. He also touches upon psychological topics, often only incidentally, in his ethical, political, and metaphysical treatises, as well as in his scientific writings, especially De Motu Animalium. The works in the Parva Naturalia are, in comparison with De Anima, empirically oriented, investigating, as Aristotle says, “the phenomena common to soul and body” (De Sensu 1, 436a6-8). This contrasts with De Anima, which introduces as a question for consideration “whether all affections are common to what has the soul or whether there is some affection peculiar to the soul itself” (De Anima i 1, 402a3-5). That is, in De Anima Aristotle wants to know whether all psychological states are also material states of the body. “This,” he remarks, “it is necessary to grasp, but not easy” (De Anima i 1, 40

Psychic Faculties

Although willing to provide a common account of the soul in these general terms, Aristotle devotes most of his energy in De Anima to detailed investigations of the soul's individual capacities or faculties, which he first lists as nutrition, perception, and mind, with perception receiving the lion's share of attention. He later also introduces desire, evidently as a discrete faculty on par with those initially introduced. The broadest is nutrition, which is shared by all natural living organisms; animals have perception in addition; and among natural organisms humans alone have mind. Aristotle maintains that various kinds of souls, nutritive, perceptual, and intellectual, form a kind of hierarchy. Any creature with reason will also have perception; any creature with perception will also have the ability to take on nutrition and to reproduce; but the converse does not hold. Thus, plants show up with only the nutritive soul, animals have both perceptual and nutritive faculties, and humans have all three. The reasons why this should be so are broadly teleological. In brief, every living creature as such grows, reaches maturity, and declines. Without a nutritive capacity, these activities would be impossible (De Anima iii 12, 434a22-434b18; cf. De Partibus Animalium iv 10, 687a24-690a10; Metaphysics xii 10, 1075a16-25). So, Aristotle concludes, psychology must investigate not only perceiving and thinking, but also nutrition.

There is some dispute about which of the psychic abilities mentioned by Aristotle in De Anima qualify as full-fledged or autonomous faculties. He evidently accepts the three already mentioned as centrally important. Indeed, he is willing to demarcate a hierarchy of life in terms of them. Even so, he also discusses two other capacities, imagination (De Anima iii 3) and desire (De Anima iii 9 and 10), and appeals to them in both his account of thinking and his philosophy of action. He does little, however, to characterize either in any intrinsic way. He evidently regards imagination as a sort of subordinate faculty, integrated in various ways with the faculties of nutrition, perception, and thought. Desire is still more complex. Despite its not occurring without the sensory faculty (De Anima iii 7 412a12-14), desire seems in the end elevated to a full capacity, primarily because of its role in the explanation of purposive behavior. His discussions of imagination and desire raise interesting questions about how Aristotle views the various capacities of soul as integrating into unified forms. They also raise questions along with his discussions of the other faculties as to how Aristotle conceives the unity of the whole soul. Some scholars seem content to characterize an Aristotelian soul as a set or sum of capacities, whereas Aristotle himself evidently demands a non-aggregative form of unity (De Anima ii 3 414b28-32, cf. iii 9 432a-b6).