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Compiled by Anthony Harrison-Barbet


(c. 580 — 500 B.C.)



Anaximenes of Miletus was probably a pupil and later a colleague of Anaximander.



[1] Anaximenes accepted the idea of a primary 'stuff' as unlimited (apeiron) but not as indeterminate [a]; he supposed it to be air (aer) [a]. This was probably because he saw breath (pneuma) as being necessary for the life of the body. He tried to explain change in terms of the processes of rarefaction and condensation [b] (or 'felting'). He said that as a result of the latter 'mobile' air turns firstly into wind, then cloud, water, earth, and stone, and thence into other substances including living things. When rarefied air becomes fire. Things can also turn back in a reverse process. In this way we have a regular progression of changes in the density of the basic 'stuff'. Air under its two active attributes, the Hot and the Cold, is thus all-pervasive and is also the 'cause' of the universe's coherence and regularity. Air therefore seems to be the ultimate source of change in the world considered as being governed by natural laws. Anaximenes also related the cosmic air to each individual soul as a microcosm [c]:

As our soul, being air, holds us together and controls us, so does wind [breath] and air enclose the whole world. [Quoted by Aetius in Placita (Opinions).]



By comparison with Anaximander Anaximenes' postulation of air as a primary principle might seem to represent a regression to the approach of Thales. However, his theory of air, unlike Anaximander's apeiron, is firmly grounded in observation of the world; and he accounts for the Hot and the Cold and all kinds of change in terms of the fundamental concepts of rarefaction and condensation without appealing to the general abstract 'opposites' of justice and retribution. But he is not completely consistent in that high and low densities of things do not always coincide with the hot-cold distinction.



G. S. Kirk, J. E. Raven, & M. Schofield, The Presocratic Philosophers, ch. IV.

R. D. McKirahan, Philosophy Before Socrates, ch. 6.

C. Joachim Classen, 'Anaximander and Anaximenes: the earliest Greek theories of change?'





[1a 1b] Common 'stuff', principle, or 'material cause' underlying change and multiplicity — 'air'; rarefaction and condensation








[1c 1g]


[6a 9b]



Limit/ indeterminate









Microcosm/ macrocosm



   Nicholas of Cusa