Chapter 19

Genus and difference have this in common, that they both contain the species and that they are both predicated univocally of species and individuals. One should furthermore know that whatever is predicated of something as of a subject, that is, univocally, will also be predicated univocally of what comes under this. In the case of equivocal predication, however, that will by no means be true. The distinguishing peculiarities of the genus as compared with the difference are: that the genus is more extensive than the differences under it and than the three other terms; that the genus contains the differences virtually; that the genus is prior by nature to the differences; that the genus is predicated of the essence of a thing, whereas the difference is predicated of its sort; that the related genus is one, whereas the differences are several; and that the genus corresponds to matter, whereas the difference corresponds to form.

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