Milesian School - Philosophy of Nature

Philosophy of Nature

These philosophers defined all things by their quintessential substance (which Aristotle, perhaps being anachronistic, called the ἀρχή / arche) of which the world was formed and which was the source of everything. Thales thought it to be water. But as it was impossible to explain some things (such as fire) as being composed of this element, Anaximander chose an unobserved, undefined element, which he called apeiron (ἄπειρον "having no limit"). He reasoned that if each of the four traditional elements (water, air, fire, and earth) are opposed to the other three, and if they cancel each other out on contact, none of them could constitute a stable, truly elementary form of matter. Consequently, there must be another entity from which the others originate, and which must truly be the most basic element of all.The notion of temporal infinity was familiar to the Greek mind in the religious conception of immortality and Anaximander's description was in terms appropriate to this conception.This arche is called "eternal and ageless"(Hippolitus I,6,I;DK B2). The unspecified nature of the apeiron upset critics, which caused Anaximenes to define it as being air, a more concrete, yet still subtle, element. Anaximenes held that by its evaporation and condensation, air can change into other elements or substances such as fire, wind, clouds, water, and earth. However, our modern concept of energy is much more similar to Anaximander's apeiron.