c. 279-207 B.C.

Greek Stoic philosopher who conceived of sound as a wave motion in air. Chrysippus succeeded Cleanthes as the third head of the Stoa in Athens and is considered its second founder. According to Diogenes Laertius, he wrote 705 books, about half of which dealt with logic and language. Chrysippus maintained that knowledge of the world is obtained through the sense organs and true perceptions can be distinguished from illusory ones through deliberation.