the way for the Platos and Aristotles of the succeeding age by his severe dialectics.  This was his mission, and he declared it by talking.  He did not lecture; he conversed.  For more than thirty years he discoursed on the principles of morality, until he arrayed against himself enemies who caused him to be put to death, for his teachings had undermined the popular system which the Sophists accepted and practised.  He probably might have been acquitted if he had chosen to be, but he did not wish to live after his powers of usefulness had passed away.

The services which Socrates rendered to philosophy, as enumerated by Tennemann, “are twofold,—­negative and positive. Negative, inasmuch as he avoided all vain discussions; combated mere speculative reasoning on substantial grounds; and had the wisdom to acknowledge ignorance when necessary, but without attempting to determine accurately what is capable and what is not of being accurately known. Positive, inasmuch as he examined with great ability the ground directly submitted to our understanding, and of which man is the centre.”

Socrates cannot be said to have founded a school, like Xenophanes.  He did not bequeath a system of doctrines.  He had however his disciples, who followed in the path which he suggested.  Among these were Aristippus, Antisthenes, Euclid of Megara, Phaedo of Elis, and Plato, all of whom were pupils of Socrates and founders of schools.  Some only partially adopted his method, and each differed from the other.  Nor can it be said that all of them advanced science.  Aristippus, the founder of the Cyreniac school, was a sort of philosophic voluptuary, teaching that pleasure is the end of life.  Antisthenes, the founder of the Cynics, was both virtuous and arrogant, placing the supreme good in virtue, but despising speculative science, and maintaining that no man can refute the opinions of another.  He made it a virtue to be ragged, hungry, and cold, like the ancient monks; an austere, stern, bitter, reproachful man, who affected to despise all pleasures,—­like his own disciple Diogenes, who lived in a tub, and carried on a war between the mind and body, brutal, scornful, proud.  To men who maintained that science was impossible, philosophy is not much indebted, although they were disciples of Socrates.  Euclid—­not the mathematician, who was about a century later—­merely gave a new edition of the Eleatic doctrines, and Phaedo speculated on the oneness of “the good.”

It was not till Plato arose that a more complete system of philosophy was founded.  He was born of noble Athenian parents, 429 B.C., the year that Pericles died, and the second year of the Peloponnesian War,—­the most active period of Grecian thought.  He had a severe education, studying mathematics, poetry, music, rhetoric, and blending these with philosophy.  He was only twenty when he found out Socrates, with whom he remained ten years, and from whom he was separated