On the Soul (Greek: Περὶ Ψυχῆς, Peri Psychēs; Latin: De Anima) is a major treatise written by Aristotle c. 350 BC. His discussion centres on the kinds of souls possessed by different kinds of living things, distinguished by their different operations. Thus plants have the capacity for nourishment and reproduction, the minimum that must be possessed by any kind of living organism. Lower animals have, in addition, the powers of sense-perception and self-motion (action). Humans have all these as well as intellect.
Aristotle holds that the soul (psyche, ψυχή) is the form, or essence of any living thing; it is not a distinct substance from the body that it is in. It is the possession of a soul (of a specific kind) that makes an organism an organism at all, and thus that the notion of a body without a soul, or of a soul in the wrong kind of body, is simply unintelligible. (He argues that some parts of the soul — the intellect — can exist without the body, but most cannot.)
In 1855, Charles Collier published a translation titled On the Vital Principle. George Henry Lewes, however, found this description also wanting.
The treatise is divided into three books, and each of the books is divided into chapters (five, twelve, and thirteen, respectively). The treatise is near-universally abbreviated “DA,” for “De anima,” and books and chapters generally referred to by Roman and Arabic numerals, respectively, along with corresponding Bekker numbers. (Thus, “DA I.1, 402a1” means “De anima, book I, chapter 1, Bekker page 402, Bekker column a [the column on the left side of the page], line number 1.)
DA I.1 introduces the theme of the treatise; DA I.2–5 provide a survey of Aristotle’s predecessors’ views about the soul
DA II.1–3 gives Aristotle's definition of soul and outlines his own study of it, which is then pursued as follows: DA II.4 discusses nutrition and reproduction; DA II.5–6 discuss sensation in general; DA II.7–11 discuss each of the five senses (in the following order: sight, sound, smell, taste, and touch—one chapter for each); DA II.