The beginning of the fifth century b.c. – the time when Greek civilization was menaced by the expanding might of the Persian Empire, and managed to save itself from being overwhelmed – is a period of some confusion for the literary historian. The materials he has to work with consist of the Victory Odes of Pindar, some other specimens of lyric poetry, and a few of Aeschylus' plays. In philosophy, we have a chancy collection of the fragments of Heraclitus, Parmenides, Anaxagoras, and Empedocles. Hardly anything else is preserved in sufficient quantity to allow a critical view to be taken of it, or even to provide background against which we can locate the works that have survived. It is possible that our histories do some injustice, by concentrating on the known names and works, to others whose efforts were at the time of equal importance. But we have no choice: we can only endeavor to make the most of the available evidence. Some have tried to supply the background that is missing from the Greek inheritance by looking at other cultures, especially those of the Near East. It is, of course, right to make the effort, and for the period when the transmission was not by written texts but oral, and when myth dominated the poetic scene, the comparisons have proved invaluable. In my opinion they have been much less successful and illuminating for the period when, with the growth of literacy, philosophy and the exact sciences were emerging from the mythical background.