ARISTOTLE'S PRIOR AND POSTERIOR ANALYTICS

THE PURE OR ASSERTORIC SYLLOGISM 27he treats it as a universal metaphysical fact that the presence ofgeneric natures in particular things is mediated by the presenceof specific forms of these generic natures. And in his theory offirst-figure syllogisms Aristotle does little more than give a logicalturn to this metaphysical doctrine. The connexion of Aristotle'stheory of syllogism with this passage of the Phaedo seems to bemade clear, as Shorey points out, by the occurrence not only ofthe word 7Tap£,vaL, a word very characteristic of the Theory ofIdeas, in Aristotelian passages, I to express the relation of predicateto subject in the propositions of a syllogism, but also of themore definite and unusual words i7TLlflp£lv ('to bring in') anduVY£7Tt.plp£tv ('to bring in along with itself') to express the introductionof the generic nature by the specific.'2The occurrence of these words in the Topics in this very specialmeaning is clear evidence of the impression which the Phaedopassage made on Aristotle's mind. But the passage does not seemto have immediately suggested to him the theory of syllogism;for the Topics passages have no reference to that. We may, however,suppose that in course of time, as Aristotle brooded over thequestion what sort of data would justify a certain conclusion, hewas led to give a logical turn to Plato's metaphysical doctrine,and to say: 'That which will justify us in stating that C is A, orthat it is not A, is that C falls under a universal B which drags thewider universal A with it, or under one which excludes A.' Thisis very easily translated into the language which he uses informulating the principle of the first figure: 3 'Whenever threeterms are so related to one another that the last is contained inthe middle as in a whole, and the middle is either contained in orexcluded from' (the same alternatives of which the Phaedo takesaccount) 'the first as in or from a whole, the extremes must berelated by a perfect syllogism.' And the fact that only the firstfigure answers to Plato's formula is the reason why Aristotle putsit in the forefront, describes only first-figure arguments as perfect(i.e. self-sufficient), and insists on justifying all others by reductionto that figure. Aristotle's translation of Plato's metaphysicaldoctrine into a doctrine from which the whole of formal logic wasto develop is a most remarkable example of the fertilization ofone brilliant mind by another.I An. Pr. 44'4, 5, 45'10; Top. I26 b 22, 25.2 Cf. Phaedo 104 e 10,105 a 3,4, d 10 with An. Pr. 52b7, Top. 144bI6, 17, 27,29, 30, 157b23' 3 An. Pr. 2Sb32-5.