[Footnote 1: We know for certain--and it is one of the evidences of the importance attached to this trivial-looking pastime--that two of the great teacher's logical treatises, the Topics and the Sophistical Refutations, were written especially for the guidance of Questioners and Respondents. The one instructs the disputant how to qualify himself methodically for discussion before an ordinary audience, when the admissions extracted from the respondent are matters of common belief, the questioner's skill being directed to make it appear that the respondent's position is inconsistent with these. The other is a systematic exposure of sophistical tricks, mostly verbal quibbles, whereby a delusive appearance of victory in debate may be obtained. But in the concluding chapter of the _Elenchi_, where Aristotle claims not only that his method is superior to the empirical methods of rival teachers, but that it is entirely original, it is the Syllogism upon which he lays stress as his peculiar and chief invention. The Syllogism, the pure forms of which are expounded in his Prior Analytics, is really the centre of Aristotle's logical system, whether the propositions to which it is applied are matters of scientific truth as in the Posterior Analytics, or matters of common opinion as in the Topics. The treatise on Interpretation, _i.e._, the interpretation of the Respondent's "Yes" and "No," is preliminary to the Syllogism, the reasoning of the admissions together. Even in the half-grammatical half-logical treatise on the Categories, the author always keeps an eye on the Syllogistic analysis.] [Footnote 2: Theaetetus, 151 E.] [Footnote 3: Gorgias, 473 D.] [Footnote 4: Hipparchus, 225 A.] [Footnote 5: In its leading and primary use, this was a mode of debate, a duel of wits, in which two men engaged before an audience. But the same form could be used, and was used, notably by Socrates, not in an eristic spirit but as a means of awakening people to the consequences of certain admissions or first principles, and thus making vague knowledge explicit and clear. The mind being detained on proposition after proposition as assent was given to it, dialectic was a valuable instrument of instruction and exposition. But whatever the purpose of the exercise, controversial triumph, or solid grounding in the first principles--"the evolution of in-dwelling conceptions"--the central interest lay in the syllogising or reasoning together of the separately assumed or admitted propositions.]