Empedocles (c.495–c.435 B.C.), Greek pre- Socratic philosopher who created a physical theory in response to Parmenides while incorporating Pythagorean ideas of the soul into his philosophy. Following Parmenides in his rejection of coming-to-be and perishing, he accounted for phenomenal change by positing four elements (his ‘roots,’ rizomata), earth, water, air, and fire. When they mix together in set proportions they create compound substances such as blood and bone. Two forces act on the elements, Love and Strife, the former joining the different elements, the latter separating them. In his cyclical cosmogony the four elements combine to form the Sphere, a completely homogeneous spherical body permeated by Love, which, shattered by Strife, grows into a cosmos with the elements forming distinct cosmic masses of earth, water (the seas), air, and fire. There is controversy over whether Empedocles posits one or two periods when living things exist in the cycle. (On one view there are two periods, between which intervenes a stage of complete separation of the elements.) Empedocles accepts the Pythagorean view of reincarnation of souls, seeing life as punishment for an original sin and requiring the expiation of a pious and philosophical life. Thus the exile and return of the individual soul reflects in the microcosm the cosmic movement from harmony to division to harmony. Empedocles’ four elements became standard in natural philosophy down to the early modern era, and Aristotle recognized his Love and Strife as an early expression of the efficient cause. See also PYTHAGORA. D.W.G.