Air as first principle
Air is both indeterminate and perceptible, satisfying Anaximander's demand and Thales' concreteness at once.
Ancient Greece & Rome · c. 586–526 BCE
Anaximenes
阿那克西美尼 · Ἀναξιμένης
Made air the first principle and explained all differences by condensation and rarefaction, giving change its first mechanism.
Milesian SchoolBirthplace: Miletus
As our soul, being air, holds us together, so breath and air surround the whole world.
Source: Aëtius 1.3.4
Anaximenes was the third and last of the Milesians, younger than Anaximander and probably his pupil. His city was destroyed by the Persians in 494 BCE, and the school ended with it.
He made the principle a concrete element again: air. This looks like a retreat to Thales but is actually an advance. Anaximander could not say how the Boundless becomes things; Anaximenes supplied a mechanism. Rarefied, air becomes fire; condensed, it becomes in turn wind, cloud, water, earth and stone. Every difference of quality is reduced to a difference of quantity, and density becomes the key to explanation.
He added that just as our soul, being air, holds us together, so breath and air enclose the whole world. It is the first analogy between macrocosm and microcosm, and it returned later in Stoicism.
Key Ideas
Condensation and rarefaction
One stuff appears as fire, wind, water or stone according to its density. The first explanatory model that reduces quality to quantity.
Soul and cosmos
The soul is the air that holds the body together, and air holds the world together. Human and cosmos share one structure.