Plutarch (De Plac. Phil. i. 3, and iv. 3) tells us that this opinion was held by Anaximenes of Miletus, the followers of Anaxagoras, and many of the Stoics. Diogenes the Cynic, as well as Diogenes of Apollonia, seems to have adopted the same opinion. See Zeller's Stoics, pp. 121 and 199.