affirmative, there will not be a syllogism: let the terms of presence be "health," "animal," "man," but of not being present with "health," "horse," "man." The same will happen in the case of particular syllogisms, for when the affirmative is pure, taken either universally, or particularly, there will be no syllogism, and this is shown in like manner through the same terms as before. But when the negative is simple, there will be a syllogism by conversion, as in the former cases. Again, if both premises be taken negative, and that which signifies simply the non-inesse be universal; from these propositions no necessity will result, but the contingent being converted as before there will be a syllogism. If however the negative be pure but particular, there will not be a syllogism, whether the other premise be affirmative or negative. Neither will there be one, when both propositions are assumed indefinite, whether affirmative, negative, or particular, and the demonstration is the same and by the same terms.
Chapter 19
If however one premise signifies the being present necessarily, but the other contingently, when the negative is necessary there will be a syllogism, wherein not only the contingent but also the simple non-inesse (may be inferred), but when the affirmative (is necessary) there will be no syllogism. For let A be assumed necessarily present with no B, but contingent to every C, then by conversion of the negative neither will B be present with any A, but A was contingent to every C, wherefore there is again a syllogism in the first figure, so that B is contingently present with no C. At the same time it is shown that neither is B present with any C, for let it be assumed to be
