Aristotle tells us expressly that the theory of the Syllogism, both demonstrative and dialectic, on which we are now about to enter, was his own work altogether and from the beginning; that no one had ever attempted it before; that he therefore found no basis to work upon, but was obliged to elaborate his own theory, from the very rudiments, by long and laborious application. In this point of view, he contrasts Logic pointedly with Rhetoric, on which there had been a series of writers and teachers, each profiting by the labours of his predecessors.[1] There is no reason to contest the claim to originality here advanced by Aristotle. He was the first who endeavoured, by careful study and multiplied comparison of propositions, to elicit general truths respecting their ratiocinative interdependence, and to found thereupon precepts for regulating the conduct of demonstration and dialectic.[2] [Footnote 1: See the remarkable passage at the close of the Sophistici Elenchi, p. 183, b. 34-p. 184, b. 9: [Greek: tau/tês de\ tê=s pragmatei/as ou) to\ me\n ê)=n to\ de\ ou)k ê)=n proexeirgasme/non, a)ll' ou)de\n pantelô=s u(pê=rche--kai\ peri\ me\n tô=n r(êtorikô=n u(pê=rche polla\ kai\ palaia\ ta\ lego/mena, peri\ de\ tou= sullogi/zesthai pantelô=s ou)de\n ei)/chomen pro/teron a)/llo le/gein, a)ll' ê)\ tribê=| zêtou=ntes polu\n chro/non e)ponou=men.]] [Footnote 2: Sir Wm. Hamilton, Lectures on Logic, Lect. v. pp. 87-91, vol. III.:--"The principles of Contradiction and Excluded Middle can both be traced back to Plato, by whom they were enounced and frequently applied; though it was not till long after, that either of them obtained a distinctive appellation. To take the principle of Contradiction first. This law Plato frequently employs, but the most remarkable passages are found in the Phædo (p. 103), in the Sophista (p. 252), and in the Republic (iv. 436, vii. 525). This law was however more distinctively and emphatically enounced by Aristotle. . . . . Following Aristotle, the Peripatetics established this law as the highest principle of knowledge. From the Greek Aristotelians it obtained the name by which it has subsequently been denominated, the _principle_, or _law_, or _axiom_, of _Contradiction_ ([Greek: a)xi/ôma tê=s a)ntipha/seôs]). . . . . The law of Excluded Middle between two contradictories remounts, as I have said, also to Plato; though the Second Alcibiades, in which it is most clearly expressed (p. 139; also Sophista, p. 250), must be admitted to be spurious. . . . . This law, though universally recognized as a principle in the Greek Peripatetic school, and in the schools of the middle ages, only received the distinctive appellation by which it is now known at a comparatively modern date."