He gradually became a logician out of his previous studies: out of metaphysics, for with him being is always the basis of thinking, and common principles, such as that of contradiction, are axioms of things before axioms of thought, while categories are primarily things signified by names; out of the mathematics of the Pythagoreans and the Platonists, which taught him the nature of demonstration; out of the physics, of which he imbibed the first draughts from his father, which taught him induction from sense and the modification of strict demonstration to suit facts; out of the dialectic between man and man which provided him with beautiful examples of inference in the Socratic dialogues of Xenophon and Plato; out of the rhetoric addressed to large audiences, which with dialectic called his attention to probable inferences; out of the grammar taught with rhetoric and poetics which led him to the logic of the proposition.
He therefore deserves the homage which Xenophon paid to him in choosing him as hero for his didactic novel.
We are comparatively well informed from Greek sources; for the earlier part of his reign from Ctesias and Xenophon (Anabasis), for the later times from Dinon of Ephesus, the historian of the Persians (from whom the account of Justin is derived), from Ephorus (whose account is quoted by Diodorus) and others.
Cyrus had 10,400 Greek hoplites and 2500 peltasts, and besides an Asiatic army under the command of Ariaeus, for which Xenophon gives the absurd number of ioo,000 men; the army of Artaxerxes he puts down at 900,000.
The history of Cyrus and of the retreat of the Greeks is told by Xenophon in his Anabasis (where he tries to veil the actual participation of the Spartans).
The idea is drawn from Aristo of Chios, and the materials largely derived from Xenophon and Plato.
The character of Cyrus is highly praised by the ancients, especially by Xenophon (cf.
They are mentioned by Herodotus among the races conquered by Croesus, and they sent an important contingent to the army of Xerxes in 480 B.C. Xenophon speaks of them as being governed by a prince of their own, without any reference to the neighbouring satraps, a freedom due, perhaps, to the nature of the country, with its lofty mountain ranges and difficult passes.
As a writer on field sports Xenophon was followed by Arrian, who in his Cynegeticus, in avowed dependence on his predecessor, seeks to supplement such deficiencies in the earlier treatise as arose from its author's unacquaintance with the dogs of Gaul and the horses of Scythia and Libya.
The silence of the Memorabilia of Xenophon must be admitted as an argument to the contrary; but the probability seems to be that Plato did not in the Phaedo altogether misrepresent the Master.