versal, (the demonstration) is through it and through the first figure, and when it is particular, both through it and through the last. In the third all are through it, but it is also clear that in the third and in the middle the syllogisms, which are not produced through them, either are not according to a circular demonstration, or are imperfect.
Chapter 8
Conversion is by transposition of the conclusion to produce a syllogism, either that the major is not with the middle, or this (the middle) is not with the last (the minor term). For it is necessary when the conclusion is converted, and one proposition remains, that the other should be subverted, for if this (proposition) will be, the conclusion will also be. But there is a difference whether we convert the conclusion contradictorily or contrarily, for there is not the same syllogism, whichever way the conclusion is converted, and this will appear from what follows. But I mean to be opposed (contradictorily) between, to every individual and not to every individual, and to a certain one and not to a certain one, and contrarily being present with every and being present with none, and with a certain one, not with a certain one. For let A be demonstrated of C, through the middle B; if then A is assumed present with no C, but with every B, B will be with no C, and if A is with no C, but B with every C, A will not be with every B, and not altogether with none, for the universal was not concluded through the last figure. In a word, we cannot subvert universally the major
