Vitae philosophorum

Diogenes of Apollonia, son of Apollothemis, was a natural philosopher and a most famous man. Antisthenes

calls him a pupil of Anaximenes; but he lived in Anaxagoras’s time. This man,[*](i.e. Anaxagoras.) so great was his unpopularity at Athens, almost lost his life, as Demetrius of Phalerum states in his Defence of Socrates.

The doctrines of Diogenes were as follows.[*](Diels (op. cit. p. 144) compares Plutarch, Strom. apud Euseb. Praep. Evang. i. 8. 13; Aëtius i. 3. 26; Theophrastus, Phys. Opin. Fr. 2.) Air is the universal element. There are worlds unlimited in number, and unlimited empty space. Air by condensation and rarefaction generates the worlds. Nothing comes into being from what is not or passes away into what is not. The earth is spherical, firmly supported in the centre, having its construction determined by the revolution which comes from heat and by the congealment caused by cold.

The words with which his treatise begins are these: At the beginning of every discourse I consider that one ought to make the starting-point unmistakably clear and the exposition simple and dignified.