Anaximander and Anaximenes: The Milesian School of Philosophy

Anaximander: The Concept of Apeiron

Anaximander was born around 610 BC and died in 545 BC. Theophrastus described Anaximander as a disciple and companion of Thales, being some fourteen years younger than him. Like Thales, he focused on practical issues related to science and is credited with drawing up a map of the Black Sea, probably for use by Milesian sailors. He sought the primary and basic element from which reality is generated, but unlike Thales, he held that this element, or arche, could not be formed by any of the known elements such as water, nor by any particular kind of matter.

If the first element was the material cause of all existence, it had to be the cause of any particular matter; therefore, this principle could not be identified with any specific substance. He concluded that the arche must be a substance unknown to us—an indeterminate, undefined, and unlimited subject which Anaximander named apeiron.

Anaximander's cosmology is dominated by the idea of a plurality of existing worlds, generated from an eternal movement by which things are separated from each other in a game of opposites—a concept common at the time that we will find in the works of other philosophers.

Anaximenes: Air as the Primary Principle

Anaximenes was born in Miletus approximately in 585 BC and died in 524 BC. He opposed Anaximander regarding the determination of the first principle, or arche, which Anaximenes considered to be air. He likely made this choice based on experience, influenced by the observation of living beings and the vital importance of the phenomenon of breathing.

In modern terminology, we can say that Anaximenes attempted to base the explanation of the qualitative on the quantitative. We find in his work an attempt to explain the mechanism of transformation of some elements into others, a detail that Thales and Anaximander did not provide. Like his predecessors, however, he insisted on asserting a material cause as the principle of the world, striving to bring unity to the diversity of observable reality.