Anaximenes of Miletus
Anaximenes of Miletus was a sixth-century BCE Greek philosopher who held that air is the fundamental substance from which all things arise.
Rarefaction and condensation: Processes in which a substance becomes less dense or more dense, changing its properties. Anaximenes used these processes to explain how air becomes fire, wind, clouds, water, earth, and stone.
Miletus: An ancient Greek city on the western coast of Anatolia, a major center of early Greek thought. Anaximenes belonged to the intellectual community associated with this city.
Theophrastus: An ancient Greek philosopher and Aristotle’s successor, known for works on philosophy and natural history. His lost account of early Greek thinkers is a major source for reports about Anaximenes.
Arche: The first principle or originating source that early Greek philosophers proposed as the basis of reality. Anaximenes’ air is a specific answer to this central philosophical question.
Air (classical element): Air as an ancient philosophical element and proposed underlying substance of the cosmos. It is the fundamental substance in Anaximenes’ account of nature.
Milesian school: A grouping of early Greek thinkers from Miletus associated with natural explanations of the cosmos. Anaximenes is commonly grouped with Thales and Anaximander as a Milesian thinker.
Simplicius of Cilicia: A sixth-century CE Neoplatonic philosopher whose commentaries preserve fragments of earlier Greek philosophy. His commentary on Aristotle transmits a key passage attributed to Anaximenes.
Monism: The view that reality is ultimately grounded in one fundamental kind of substance or principle. His account explains the world through a single underlying substance.
Cosmology of Anaximenes: Anaximenes’ account of the structure and origin of the cosmos, grounded in air and its transformations. His theory extends the transformations of air to the formation and support of the world.
Anaximander: A sixth-century BCE Greek philosopher who proposed the apeiron, or indefinite, as the origin of things. Anaximander’s proposal preceded Anaximenes’ alternative account of a definite underlying substance.