He first studied philosophy under Anaxagoras, and next under Archelaus, the natural philosopher. But finding that all these vain speculations concerning natural objects served no useful purpose, and had no influence in rendering the philosopher a better man, he devoted himself to the study of ethics; and (as Cicero, in the third book of his Tusculan Questions, observes) may be said to be the founder of moral philosophy among the Greeks. In the first book, speaking of him still more particularly and more extensively, he expresses himself thus: "It is my opinion (and it is an opinion in which all are agreed) that Socrates was the first who, calling off the attention of philosophy from the investigation of secrets which nature has concealed (but to which alone all preceding philosophers had attached themselves), engaged her in those things which concern the duties of common life; his object was to investigate the nature of virtue and vice; and to point out the characteristics of good and evil; saying, that the investigation of celestial phenomena was a subject far above the reach of our powers; and that even were they more within the reach of our faculties, it could have no influence in regulating our conduct." That part of philosophy, then, whose province is the cultivation of morals, and which embraces every age and condition of life, he made his only study. This new mode of philosophizing was the better received on this account, that he who was the founder of it, fulfilling with the most scrupulous care all the duties of a good citizen, whether in peace or in war, enforced by example the precepts which he taught. Of all the philosophers who have acquired celebrity, he (as Lucian in his dialogue of the Parasite remarks) was the only one that ever subjected himself to the hardships of war. He served two campaigns, in both of which, though unsuccessful, he served in person and exhibited a manly courage. In the one, he saved the life of Xenophon, who when retreating, had fallen from his horse and would have been killed by the enemy, had not Socrates taking him upon his shoulders, removed him from the danger and carried him several furlongs, till his horse, which had run off, was brought back. This fact is related by Strabo. In his other campaign, the Athenians having been entirely defeated and put to flight, Socrates was the last to retreat, and showed such a stern aspect that the pursuers of those who fled, seeing him every moment ready to turn upon them, never had the boldness to attack him. This testimony is given him by Athenaeus.