He probably might have been acquitted if he had chosen it, but he did not wish to live after his powers of usefulness had passed away. He opened to science new matter and a new method, as a basis for future philosophical systems. He was a "colloquial dialectician," such as this world has never seen, and may never see again. He was a skeptic respecting physics, but as far as man and society are concerned, he thought that every man might and ought to know what justice, temperance, courage, piety, patriotism, etc., were, and unless he did know what they were he would not be just, temperate, etc. He denied that men can know that on which they have bestowed no pains, or practice what they do not know. "The method of Socrates survives still in some of the dialogues of Plato, and is a process of eternal value and universal application. There is no man whose notions have not been first got together by spontaneous, unartificial associations, resting upon forgotten particulars, blending together disparities or inconsistencies, and having in his mind old and familiar phrases and oracular propositions of which he has never rendered to himself an account; and there is no man who has not found it a necessary branch of self-education to break up, analyze, and reconstruct these ancient mental compounds." [Footnote: Grote has written very ably, and at unusual length, respecting Socrates and his philosophy. Thirlwall has also reviewed Hegel and other German authors on Socrates' condemnation. Ritter has a full chapter of great value. See Donaldson's continuation of Muller. The original sources of knowledge respecting Socrates are found chiefly in Plato and Xenophon. Cicero may be consulted in his _Tusculan Questions_.] The services which he rendered to philosophy, as enumerated by Tennemann, [Footnote: Tennemann; Schliermacker, _Essay on the Worth of Socrates as a Philosopher_, translated by Bishop Thirlwall, and reprinted in Dr. Wigger's _Life of Socrates_.] "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."