Anaximenas

Anaximenes of Miletus was an ancient Greek philosopher from the Ionian school of thought, active in the 6th century BCE. He is known as the third of the Milesian philosophers, following Thales and Anaximander. Anaximenes proposed air as the fundamental substance, or arche, from which all other things originate. He believed that this primordial air could transform into other substances through processes of rarefaction and condensation.

According to Anaximenes, when air becomes rarefied, it heats up and turns into fire. When it condenses, it cools down and becomes wind, then cloud, water, earth, and finally stone. This mechanism of change explained the diversity of the material world from a single underlying principle. His ideas represented a significant step in early Greek natural philosophy, attempting to provide a rational explanation for cosmic origins and transformations without recourse to mythology. While his theories were ultimately superseded by later thinkers, Anaximenes' concept of a material arche and his understanding of change through physical processes were influential. He is often credited with moving philosophical inquiry towards more empirical and observable phenomena.