Anaximenes

Anaximenes of Miletus (roughly 586–526 BCE) was a Pre-Socratic Greek philosopher associated with the Milesian school. He is usually considered the third major figure in the Milesian tradition, following Thales and Anaximander, and is often described as a pupil or successor of Anaximander. Based in Ionia, he contributed to the early development of natural philosophy by seeking a single, underlying principle for all things.

Anaximenes proposed that air (aer) is the arche, the basic substance from which everything arises. He argued that all changes in the world can be explained by processes of thinning (rarefaction) and thickening (condensation) of air. In his view, when air is rarefied it becomes fire and wind; when it condenses, it forms clouds, then water, and finally earth and stones. This account presents a continuum of transformation rather than a jump between discrete elements.

In addition to his account of material change, Anaximenes offered naturalistic explanations for various phenomena, including weather and celestial motions, grounding them in the behavior of air. The earth was conceived as flat and supported by air, while celestial bodies were explained through the same physical principles.

The surviving information about Anaximenes comes mainly from later authors who preserved fragments and summaries of his thought. Although few direct writings survive, his ideas helped shape later debates in early Greek philosophy and contributed to the move toward naturalistic explanations of the world.