The cultivation of the art of oratory among the Athenians was due to a combination of the natural eloquence displayed by the Athenian statesmen, and especially by Pericles, with the rhetorical studies of the sophists, who exercised a greater influence on the culture of the Greek mind than any other class of men, the poets excepted. The sophists, as their name indicates, were persons who made knowledge their profession, and undertook to impart it to every one who was willing to place himself under their guidance; they were reproached with being the first to sell knowledge for money, for they not only demanded pay from those who came to hear their lectures, but they undertook, for a certain sum, to give young men a complete sophistical education. Pupils flocked to them in crowds, and they acquired such riches as neither art nor science had ever before earned among the Greeks. If we consider their doctrines philosophically, they amounted to a denial or renunciation of all true science. They were able to speak with equal plausibility for and against the same position; not in order to discover the truth, but to show the nothingness of truth. In the improvement of written composition, however, a high value must be set on their services. They made language the object of their study; they aimed at correctness and beauty of style, and they laid the foundation for the polished diction of Plato and Demosthenes. They taught that the sole aim of the orator is to turn the minds of his hearers into such a train as may best suit his own interest; that, consequently, rhetoric is the agent of persuasion, the art of all arts, because the rhetorician is able to speak well and convincingly on every subject, though he may have no accurate knowledge respecting it. The Peloponnesian war, which terminated in the downfall of Athens, was succeeded by a period of exhaustion and repose. The fine arts were checked in their progress, and poetry degenerated into empty bombast. Yet at this very time prose literature began a new career, which led to its fairest development.