this in the terms, thus A (may be) with every B but with no C, or with every C and with no B, or with the whole of the one, but not with the whole of the other; and again, we may convert this as to the terms. It will be the same also in the third figure, so that it is clear in how many ways and in what figures it is possible for a syllogism to arise through opposite propositions.
But it is also manifest that we may infer a true conclusion from false premises, as we have observed before, but from opposites we cannot, for a syllogism always arises contrary to the fact, as if a thing is good, (the conclusion will be,) that it is not good, or if it is an animal, that it is not an animal, because the syllogism is from contradiction, and the subject terms are either the same, or the one is a whole, but the other a part. It appears also evident, that in paralogisms there is nothing to prevent a contradiction of the hypothesis arising, as if a thing is an odd number, that it is not odd, for from opposite propositions there was a contrary syllogism; if then one assumes such, there will be a contradiction of the hypothesis. We must understand, however, that we cannot so conclude contraries from one syllogism, as that the conclusion may be that what is not good is good, or any thing of this kind, unless such a proposition is immediately assumed, as that every animal is white and not white, and that man is an animal. But we must either presume contradiction, as that all science is opinion, and is not opinion, and afterwards assume that medicine is a science indeed, but is no opinion, just as Elenchi are produced, or (conclude) from two syllo-
