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date: 27 June 2022



  • Charles H. Kahn


  • Philosophy

Anaximenes (1), of Miletus (traditional floruit 546–525 bce) followed in the footsteps of Anaximander in composing a treatise in Ionian prose in which he developed a world system on the basis of an infinite or unlimited principle, which he identified as aēr. His system differed from that of his predecessor in several respects. Instead of suspending the earth in the centre of the universe by cosmic symmetry, he supported it from below by cosmic air. And instead of leaving the infinite starting-point for world formation indeterminate in nature, he specified it as elemental air, which he probably conceived as a kind of vital world-breath that dominates the world order as our own breath-soul rules over us. Anaximenes also offered a mechanistic explanation for world formation and change in terms of the condensation and rarefaction of the air. Air becomes fire by rarefaction; by motion it becomes wind; by condensation it becomes water and, by more condensation, earth and stones.

It was the Milesian cosmology as reformulated by Anaximenes that became standard for Ionian natural philosophy in the 5th cent. Heraclitus (1) reacts against this system by replacing air with fire. Anaxagoras and Democritus follow Anaximenes in regarding the earth as a flat disc supported by air. Diogenes (1) of Apollonia, the most conservative 5th-cent. physicist, retains the cosmic air as divine principle of life and intelligence, controlling the world-order.


  • H. Diels and W. Kranz, Fragmente der Vorsokratiker, 1. 90 ff.
  • Burnet, Early Greek Philosophy 72 ff.
  • G. S. Kirk, J. E. Raven, and M. Schofield, The Presocratic Philosophers, 143 ff.
  • W. K. C. Guthrie, History of Greek Philosophy 1. 115 ff.
  • J. Barnes, The Presocratic Philosophers 1 (1979), 43 ff.
  • M. Schofield, in C. C. W. Taylor (ed.), Routledge History of Philosophy vol. 1 (1997): Anaximenes 64–68.