There are four ideas about the origin .of the syllogistic. Our aim is to trace the making of Aristotle's Logic, critically examining these ideas. We assume that APr presupposes Top  SE and that Top II-VII 2 comes earlier than Top I, VII 3-VIII, SE. In the latter, "συλλογισμοs" (=syllogism) comes: to be used technically and theorized as dialectical syllogism. We examine first Plato's theory of division. Le Blond and others derive the ground of their idea about the origin of the Syllogistic,entirely from the sentence that the division is a weak syllogism. They interpret that Aristotle has established his syllogistic by his critical consideration of this weak syllogism. APr I 31 and APo II 5 where he criticizes Plato's division theory are different from one another in the aspect 'of argument. In APr I 31, he simply takes issue with all those who insist that the division has a power of the demonstration, and shows by trying, to syllogize the division that it cannot demonstrate anything. So he has no hesitation to say that the division is a syllogism. In APo II 5, while evaluating highly division's peculiar function, he clearly says that the division is not a syllogism. So "a weak syllogism" is mere irony. The syllogistic is not dans le prolongement of the division. But the division might be able to be arranged in the theory of the origin only in the sense of affecting the making of the dialectical syllogism in Top and SE.