Scant Evidence.

Greek philosophy has survived only in tantalizing fragments. The works of only one philosopher, Plato, have survived in their entirety. Much of Aristotle has been lost, and the scientific and philosophic treatises that have survived were not written for publication. Socrates who lived in Athens in the fifth century B.C.E., wrote nothing, although he gave Greek philosophy a new direction. Modern knowledge of him is dependent on two very different disciples, Plato and Xenophon, and a burlesque of his teachings by the comic poet, Aristophanes. The works of the philosophers before Socrates, the so-called "Presocratics" who speculated about the nature of the universe, are all lost. They are known by reputation, and by fragments of what they wrote, which are mostly quotations by later writers. One late writer in particular, Diogenes Laertius, wrote a work that is indispensable to modern...