Diogenes Apolloniates or Diogenes of Apollonia (c. 460 BC), Greek natural philosopher, was a native of Apollonia in Crete.

Although of Dorian stock, he wrote in the Ionic dialect, like all the physiologi (physical philosophers). There seems no doubt that he lived some time at Athens, where it is said that he became so unpopular (probably owing to his supposed atheistic opinions) that his life was in danger.

The views of Diogenes are transferred in The Clouds (264 if.) of Aristophanes to Socrates. Like Anaximenes, he believed air to be the one source of all being, and all other substances to be derived from it by condensation and rarefaction. His chief advance upon the doctrines of Anaximenes is that he asserted air, the primal force, to be possessed of intelligence—"the air which stirred within him not only prompted, but instructed. The air as the origin of all things is necessarily an eternal, imperishable substance, but as soul it is also necessarily endowed with consciousness."

In fact, he belonged to the old Ionian school, whose doctrines he modified by the theories of his contemporary Anaxagoras, although he avoided his dualism. His most important work was De natura, of which considerable fragments are extant (chiefly in Simplicius); it is possible that he wrote also Against the Sophists and On the Nature of Man, to which the well-known fragment about the veins would belong; possibly these discussions were subdivisions of his great work.

This entry was originally from the 1911 Encyclopedia Britannica.