Chapter 15

Every predicate is either more extensive than its subject or co-extensive with it, but it is never less extensive. It is more extensive when more general things are predicated of more particular ones. The more general, then, are the superior, whereas the more particular are the inferior. And the most general thing of all is the being, for which reason it is predicable of all things. For, substance is called a being, and so is accident called a being. But we cannot say that the being is substance, because not only is substance being, but so is accident. Genera, likewise, are predicable of their species, because they are more general; but the species are not predicable of their genera, because they are less general than their genera. Thus, substance is predicated of the animal, and the animal is predicated of man. This is because the animal is a substance and man is an animal. This is not, however, convertible, because, although every man is an animal, not every animal is a man—for the horse and the dog are animals, too. Moreover, not every substance is an animal, for stone and wood are substances which are not animals. Similarly, the species is predicable of the individuals contained in it, that is to say, of the individual substances, because the species is more general. But the individual, that is to say, the individual substance, is not predicable of the species, because the individual substance is more particular than its species. Thus, Peter is a man and Paul is a man, but not every man is Peter or Paul, because there are other persons contained in the human species. The differences also are predicable of the species in which they inhere and of their individuals. This is because the differences are more general than the species. Thus, the rational is more general than the species of man, because, although every man is rational, not every rational being is a man. Although the angel also is rational, he is not a man. Such, then, is the predicate which is more extensive.

The predicate, on the other hand, is co-extensive with its subject, when it is convertible. Thus, properties are predicated of the species of which they are properties; and the species are predicated of their properties. For every man is capable of laughter and everything that is capable of laughter is a man. Even though a monkey may also be said to laugh, it does not l