contrary; whole sentences then, must be considered in the manner stated, but according to parts, thus. In the first place, (it must be shown) that the assigned genus is rightly assigned, for if the contrary be in the contrary genus, but the thing proposed is not in the same, it will clearly be in the contrary (genus), since contraries must of necessity either be in the same, or in contrary genera. We also think that contrary differences are predicated of contraries, as of white and black, for the one is dissipative, the other is collective of vision. Wherefore, if contraries are predicated of a contrary, the assigned (differences) would be predicated of the thing proposed, so that since both genus and differences are rightly assigned, it is evident that what is assigned, will be a definition. Or it is not necessary that contrary differences should be predicated of contraries, unless they should be contraries in the same genus, yet of those of which the genera are contrary, there is nothing to prevent the same difference being predicated of both; e. g. of justice and injustice, for the one is a virtue, but the other a vice of the soul, so that the word "of the soul," being a difference, is predicated of both, since there is of the body also, a virtue and a vice. Nevertheless, this at least is true, that the differences of contraries are either contrary or the same; if then a contrary be predicated of a contrary, but not of this, it is evident that the difference adduced, will be predicated of this. In short, since definition consists of genus and differences, if the definition of the contrary be manifest, the definition also of the thing proposed, will be manifest. For as what is contrary, is either in the same, or in a contrary genus, and likewise either contrary or the same differences, are predicated of contraries, it is evident, that the same genus will be predicated of the thing proposed, which was also of the contrary; but the differences are contrary, either all or some, yet the remainder are the same, or on the contrary, the differences are the same, but
