is opposed to (being present) not with a certain one according to expression only. But of these I call such contraries as are universal, viz. the being present with every, and (the being present) with none, as for instance, that every science is excellent to no science is excellent, but I call the others contradictories.
In the first figure then there is no syllogism from contradictory propositions, neither affirmative nor negative; not affirmative, because it is necessary that both propositions should be affirmative, but affirmation and negation are contradictories: nor negative, because contradictories affirm and deny the same thing of the same, but the middle in the first figure is not predicated of both (extremes), but one thing is denied of it, and it is predicated of another; these propositions however are not contradictory.
But in the middle figure it is possible to produce a syllogism both from contradictories and from contraries, for let A be good, but science B and C; if then any one assumed that every science is excellent, and also that no science is, A will be with every B, and with no C, so that B will be with no C, no science therefore is science. It will be the same also, if, having assumed that every science is excellent, it should be assumed that medicine is not excellent, for A is with every B, but with no C, so that a certain science will not be science. Likewise if A is with every C, but with no B, and B is science, C medicine, A opinion, for assuming that no science is opinion, a person would have assumed a certain science to be opinion. This however differs from the former in the conversion of the terms, for before the affirmative was joined to B, but now it is to C. Also in a similar manner, if one premise is not universal, for it is always the middle which is predicated negatively of the one and affirmatively of the other. Hence it happens that contradictories are
