Anaximenes of Miletus
Greek philosopher, born in Miletus, Asia Minor (now Turkey). A follower of *Anaximander, he addressed himself to the question of the original nature of all things. He believed that origin to be air, for by processes of condensation and rarefaction air could be transformed into all other things. Condensation of air produces water, and eventually earth, rarefaction of air produces fire. *Plutarch tells us that Anaximenes demonstrated this truth by experiment. If we expel air from our mouths, it becomes cold if we exhale under pressure, whereas if we open our mouths wide, it is hot.
Anaximenes probably thought of air as made up of small, separate particles. He believed in the infinity of worlds, and thought that each was formed by processes of condensation and rarefaction. He thought the earth was at the centre of things, and that both the sun and moon had been formed out of fire.