The Greek philosopher Anaxagoras (ca. 500-ca. 428 BC) was the first to formulate a molecular theory of matter and to regard the physical universe as subject to the rule of rationality or reason.

Anaxagoras was born on the Ionian coast of Asia Minor in the town of Clazomenae, near Smyrna (now Izmir, Turkey). Nothing is known about his life before the age of 20, when he began to study philosophy. About 462 he moved to Athens, which was rapidly becoming an attractive cultural center. Anaxagoras was the first philosopher to take up residence in Athens. His teachings influenced the playwright Euripides, but his most famous pupil was Pericles, who dominated the political life of Athens during the 30 years Anaxagoras lived there.

Anaxagoras did not believe that the sun and moon were divinities, as the Greeks did, and he was prosecuted for his teachings. He returned to Asia Minor to a town...