Anaximander (c.612–545 B.C.), Greek philosopher and cosmologist, reputedly the student and successor of Thales in the Milesian school. He described the cosmos as originating from apeiron (the boundless) by a process of separating off; a disk-shaped earth was formed, surrounded by concentric heavenly rings of fire enclosed in air. At ‘breathing holes’ in the air we see jets of fire, which are the stars, moon, and sun. The earth stays in place because there is no reason for it to tend one way or another. The seasons arise from alternating periods where hot and dry or wet and cold powers predominate, governed by a temporal process (figuratively portrayed as the judgment of Time). Anaximander drew a map of the world and explained winds, rain, and lightning by naturalistic hypotheses. He also described the emergence of life in a way that prefigures the theory of evolution. Anaximander’s interest in cosmology and cosmogony and his brilliant conjectures set the major questions for later pre- Socratics. See also APEIRON , MILESIAN. D.W.G.