It was not till the superior talents of Pericles had quieted the storms of war and faction that science, which had in the interval received great improvement among the Asian Greeks, revived at Athens with new vigour. Anaxagoras of Clazomenæ, the preceptor and friend of Pericles, bred in all the learning of the Ionian school, is said first to have introduced what might properly be called philosophy there. To him is attributed the first introduction in European Greece of the idea of one eternal, almighty, and all-good Being, or, as he is said, after Thales, to have expressed himself, a perfect mind, independent of body, as the cause or creator of all things. The gods received in Greece, of course, were low in his estimation; the sun and moon, commonly reputed divinities, he held to be mere material substances, the sun a globe of stone, the moon an earth, nearly similar to ours. A doctrine so repugnant to the system on which depended the estimation of all the festivals, processions, sacrifices, and oracles, which so fascinated the vulgar mind, was not likely to be propagated without reprehension. Even the science which enabled men to calculate an eclipse was offensive, inasmuch as it lowered the importance, and interfered with the profits, of priests, augurs, interpreters, and seers. An accusation of impiety was therefore instituted against Anaxagoras; the general voice went with the prosecutors; and all that the power and influence of Pericles could do for his valued friend, was to procure him means of escape from Attica. But while physical and metaphysical speculation engaged men of leisure, other learning had more attraction for the ambitious and needy. Athens always was the great field for acquiring fame and profit in this line; yet those who first attained eminence in it were foreigners there, Gorgias of Leontini in Sicily, Prodicus of the little island of Ceos, and Hippias of Elis. All these are said to have acquired considerable riches by their profession. Their success invited numbers to follow their example; and Greece, but far more especially Athens, shortly abounded with those who, under the name of sophists, professors of wisdom, undertook to teach every science. The scarcity and dearness of books gave high value to that learning which a man with a well-stored mind, and a ready and clear elocution could communicate. None, without eloquence, could undertake to be instructors; so that the sophists, in giving lessons of eloquence, were themselves the example. They frequented all places of public resort, the agora, the public walks, the gymnasia, and the porticoes; where they recommended themselves to notice by an ostentatious display of their abilities, in disputation among one another, or with whoever would converse with them.