Milesian School of Ancient Greek Philosophy Texts

Miletus, a Greek city of Ionia, produced the first philosophers of the Greek world. In the 6th century BCE Thales was followed there by his associates Anaximander and Anaximenes, and the three together make up what is called the Milesian tradition.

Their shared undertaking was to name the ἀρχή, the fundamental source and material of everything, and to hold that all things arise through transformations of this single underlying stuff. Each proposed a different candidate. Thales named water. Anaximander argued for the ἄπειρον, an indefinite and boundless originative stuff. Anaximenes named air, and gave the clearest mechanism of change: rarefaction, by which air becomes fire, and condensation, by which it becomes wind, cloud, water, earth, and stone in turn.

The Milesians pictured the cosmos as a self-regulating system. Anaximander described a mechanical equilibrium in which opposites such as hot and cold encroach on one another and pay the penalty for their injustice, and he offered a non-mythological model of the heavens, with celestial bodies as rings of fire enclosed in mist. Thales (c. 624–c. 546 BCE) is credited with predicting a solar eclipse and with bringing geometrical principles to Greece; Anaximander (c. 610–c. 546 BCE) wrote the first known prose treatise on nature, drew a map of the inhabited world, and proposed that life originated in water. Anaximenes (c. 586–c. 526 BCE), a younger associate of Anaximander, supplied the tradition's fullest account of physical change.

The tradition's direct activity at Miletus ended when the Persians sacked the city in 494 BCE, but its method — the search for a natural ἀρχή — shaped the later Presocratic thinkers, reaching the Pythagoreans, Heraclitus, and the atomists.