Anaximenes of Miletus (fl. c.545 B.C.), Greek philosopher, a pre-Socratic who, following in the tradition of the Milesians Thales and Anaximander, speculated about cosmology and meteorology. The source (arche) of the cosmos is air (aer, originally mist), which by a process of rarefaction becomes fire, and by a process of condensation becomes wind, clouds, water, earth, and stones. Air is divine and causes life. The earth is flat and rides on a cushion of air, while a heavenly firmament revolves about it like a felt cap. Anaximenes also explained meteorological phenomena and earthquakes. Although less innovative than his predecessor Anaximander, he made progress in naturalistic explanations by appealing to a quantitative process of rarefaction and condensation rather than to mythical processes involving quasi-personal agents.
D.W.G.