Version: v1, Published online: 1998
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17. Soul and body
Aristotle’s treatise On the Soul is placed among the works on natural philosophy, but should be read with Metaphysics VII–IX. In Aristotle’s view, disputes about soul and body are simply a special case of the more general disputes about form and matter. He rejects both the Presocratic materialist assumption that the soul is simply non-organic matter, and the Platonic dualist claim that it must be something entirely non-bodily. He argues that soul is substance because it is the form of a natural body, and that the body is the matter informed by the soul. Although the soul is a substance distinct from the non-organic body (the collection of non-organic matter belonging to a living organism; see §13), it is not immaterial (if being immaterial excludes being composed of matter), nor is it independent of some non-organic body or other.
Aristotle assumes that the soul is the primary principle of life, and hence that it distinguishes the living from the non-living. A living organism is nourished, grows and diminishes, through itself – from a causal origin within itself rather than from the action of external agents. A living organism must, therefore, be teleologically ordered, since (for Aristotle) nutrition and growth cannot be understood without appeal to final causation (see Teleology).
If life must be conceived teleologically, and the soul is the primary principle of life, then the soul is form rather than matter. For the primary principle is whatever explains our vital activities; since these are goal-directed activities, their explanation must refer to the goal-directed features of the subject, and so to the form rather than the matter. If the soul is what we live by primarily, it must be the final cause of the body, and so a formal, not a material, aspect of the subject. Soul must, therefore, be substance as form.
Aristotle attributes to the soul the features of substantial form (see §13). (1) It is a substance that is irreducible to a material non-organic body (remote matter); to that extent the soul is incorporeal, and not just some ordinary material stuff. (2) It is the source of unity that makes a heap of material constituents into a single organism. For a collection of flesh and bones constitutes a single living organism in so far as it is teleologically organized; the activities of the single organism are the final cause of the movements of the different parts. Since a single organism has a single final cause, it has a single soul and a single body. (3) The identity and persistence of the soul determine the identity and persistence of the creature that has it. If something has a soul in so far as it has life, then Socrates perishes if and only if his soul does. The truth of this Platonic claim (Phaedo 115c–e) does not imply Platonic dualism. (4) The definition of a soul must mention the proximate material subject (the organic body and its parts) whose capacities are actualized in the functions of the organism (Metaphysics 1036b28–30). A soul must be non-coincidentally connected to a specific sort of organic body (On the Soul 407b20–4).
Some of the puzzles in Aristotle’s doctrine of substantial form arise in his doctrine of soul and body. If, for instance, he recognizes particular substantial forms, then he also recognizes (as the previous paragraph assumes) the individual souls of Socrates and Callias; if, however, he recognizes only one substantial form for each species, then he recognizes only one soul for human beings, another for horses, and so on.
Since the soul is the form of the living body, an account of the different ‘parts’ or ‘capacities’ (or ‘faculties’; dynameis) of the soul does not describe the different physiological processes underlying the different activities of a living organism, but describes their formal and goal-directed aspects. Aristotle describes the capacities that distinguish the different types of souls: nutrition (characteristic of plants), perception and appearance (characteristic of animals) and rational thought (characteristic of rational animals) (see Psychē). He describes some of the physiological basis of these psychic capacities in the shorter treatises on natural philosophy, including the Parva Naturalia, the Movement of Animals, and the Progression of Animals.
Irwin, T.H.. Soul and body. Aristotle (384–322 BC), 1998, doi:10.4324/9780415249126-A022-1. Routledge Encyclopedia of Philosophy, Taylor and Francis, https://www.rep.routledge.com/articles/biographical/aristotle-384-322-bc/v-1/sections/soul-and-body-1.
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