On the Soul (Greek Περὶ Ψυχῆς, Peri Psychēs; Latin De Anima) is a major treatise written by Aristotle c. 350 BC. Although its topic is the soul, it is not about spirituality but rather a work in what might best be described as biopsychology, a description of the subject of psychology within a biological framework. 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.