Diogenes of Apollonia

Not much information about his life has survived, but it is likely that he was younger than the Ionian philosophers. Diogenes himself held the idea that the basic fluid is air. He based his teachings on Anaximenes and Anaxagoras.

In his works, Díogenés followed the procedure of laying down an undeniable principle at the beginning and giving a simple and serious interpretation. For him, that principle is air. Air, according to him, is infinite, eternal, immeasurable, omnipotent, omniscient, and pervading everything. Air is said to animate even the universe, and the soul is of an airy nature.

Interestingly, Diogenes considered pure and dry air to be the ideal conditions for thought. If there was moisture in the air, it made the necessary conditions worse. The human senses are affected by the mixing of the air with the blood and this affects whether one feels pain or pleasure.

Among other things, he also taught that there are several worlds at the same time that are similar to ours.