Chapter 9
It sometimes happens also that when one proposition is necessary, a necessary syllogism arises, not however from either proposition indifferently, but from the one that contains the greater extreme. For example, if A is assumed to be necessarily present or not present with B, but B to be alone present with C, for the premises being thus assumed, A will necessarily be present or not with C; for since A is or is not necessarily present with every B, but C is something belonging to B, C will evidently of necessity be one of these. If, again, A B (the major) is not necessary, but B C (the minor) is necessary, there will not be a necessary conclusion, for if there be, it will happen that A is necessarily present with a certain B, both by the first and the third figure, but this is false, for B may happen to be a thing of that kind, that A may not be present with any thing of it. Besides, it is evident from the terms, that there will not be a necessary conclusion, as if A were "motion," B "animal," and C "man," for "man" is necessarily "an animal," but neither are "animal" nor "man" necessarily "moved;" so also if A B is negative, for there is the same demonstration. In particular syllogisms, however, if the universal is necessary, the conclusion will also be necessary, but if the particular be, there will not be a necessary conclusion, neither if the universal premise be negative nor affirmative. Let then, in the first place, the universal be necessary, and let A be necessarily present with every B,
