[Footnote 6: Like every other fashion, Yes-and-No Dialectic had its period, its rise and fall. The invention of it is ascribed to Zeno the Eleatic, the answering and questioning Zeno, who flourished about the middle of the fifth century B.C. Socrates (469-399) was in his prime at the beginning of the great Peloponnesian War when Pericles died in 429. In that year Plato was born, and lived to 347, "the olive groves of Academe" being established centre of his teaching from about 386 onwards. Aristotle (384-322), who was the tutor of Alexander the Great, established his school at the Lyceum when Alexander became king in 336 and set out on his career of conquest. That Yes-and-No Dialectic was then a prominent exercise, his logical treatises everywhere bear witness. The subsequent history of the game is obscure. It is probable that Aristotle's thorough exposition of its legitimate arts and illegitimate tricks helped to destroy its interest as an amusement.] [Footnote 7: Hamilton's _Lectures_, iii. p. 37.] II.--LOGIC AS A PREVENTIVE OF ERROR OR FALLACY.--THE INNER SOPHIST. Why describe Logic as a system of defence against error? Why say that its main end and aim is the organisation of reason against confusion and falsehood? Why not rather say, as is now usual, that its end is the attainment of truth? Does this not come to the same thing? Substantially, the meaning is the same, but the latter expression is more misleading. To speak of Logic as a body of rules for the investigation of truth has misled people into supposing that Logic claims to be an art of Discovery, that it claims to lay down rules by simply observing which investigators may infallibly arrive at new truths. Now, this does not hold even of the Logic of Induction, still less of the older Logic, the precise relation of which to truth will become apparent as we proceed. It is only by keeping men from going astray and by disabusing them when they think they have reached their destination that Logic helps men on the road to truth. Truth often lies hid in the centre of a maze, and logical rules only help the searcher onwards by giving him warning when he is on the wrong track and must try another. It is the searcher's own impulse that carries him forward: Logic does not so much beckon him on to the right path as beckon him back from the wrong. In laying down the conditions of correct interpretation, of valid argument, of trustworthy evidence, of satisfactory explanation, Logic shows the inquirer how to test and purge his conclusions, not how to reach them.