ARISTOTLE'S PRIOR AND POSTERIOR ANALYTICS

THE PURE OR ASSERTORIC SYLLOGISM 35way described in the fourth figure. We found a partial unnaturalnessin the second and third figures, due to the fact that one ofthe extreme terms must become predicate instead of subject in thesecond figure, and one of the extreme tenns subject instead ofpredicate in the third; the fourth figure draws a completelyunnatural conclusion where a completely natural conclusion ispossible. From All M is P, All 5 is M, instead of the naturalfirst-figure conclusion, All 5 is P, in which P and 5 preserve theirroles of predicate and subject, it concludes Some P is 5, whereboth terms change their roles.A distinction must be drawn, however, between the first threemoods of the fourth figure and the last two. With the premissesof Bramantip (All A is B, All B is C) the only natural conclusionis All A is C, with those of Camenes the only natural conclusion isNo A is C, with those of Dimaris it is Some A is C ; and if we wantinstead from the given premisses to deduce respectively Some Cis A, No C is A, Some C is A, the natural way to do this is to drawthe natural conclusions, and then convert these. And this is howAristotle actually treats the matter, instead of treating Bramantip,Camenes, Dimaris as independent moods. I The position withregard to Fesapo (No A is B, All B is C, Therefore some C is notA) and Fresison (No A is B, Some B is C, Therefore some C isnot A) is different; here no first-figure conclusion can be drawnfrom the premisses as they stand; for if we change the order of thepremisses to get them into the first-figure form, we get a negativeminor premiss, which in the first figure can yield no conclusion.To get first-figure premisses which will yield a conclusion we mustconvert both premisses, and then we get in both cases No B isA, Some C is B, Therefore some C is not A. This also Aristotlepoints ouU Thus he recognizes the validity of all the inferenceswhich later logicians treated as moods of a fourth figure, buttreats them, more sensibly, by way of two appendixes to his treatmentof the first figure.There is a certain misfit between Aristotle's definition of syllogismand his actual account of it. His definition is a definition ofthe meaning of the word as it was occasionally already used inordinary Greek, and it is a definition which might stand as adefinition of inference in general-av,u0ywfLO' iun ..\oyo, iv cpn8lvTwv nvwv ;npov n TWV KHfLlvwv i~ c:ivtfYK7}' aVfL{3a{vEL Tip TaVTaElvaL.3 But in his actual usage he limits av"\"OYLufLO, to inferenceI An. Pr. 53a3-12. • 29"19-26. 3 24 bl 8-20.