De ente et essentia

Having seen these things, it is clear how essence is found in different things. For there are three modes of possessing essence in substances. One is like God, whose essence is his very being; and therefore some philosophers say that God does not have a quiddity or essence, because his essence is nothing other than his being. From this it follows that he is not in a genus, because everything that is in a genus must have a quiddity distinct from its being, since the quiddity or nature of the genus or species is not distinguished according to the nature's intelligible account in those of which it is the genus or species, whereas being is diverse in diverse things.

Nor, if we say that God is being alone, need we fall into the error of those who said that God is that universal being by which each thing formally is. For this being which God is has the condition that no addition can be made to it; hence, through its very purity, it is being distinct from every other being. For this reason, in the commentary on proposition nine of the Book of Causes it is said that the individuation of the first cause, which is being alone, is through its pure goodness. Now, just as being, according to its intelligible account, does not include any addition, so neither does its intelligible account include the exclusion of an addition. For if being were something common, something would have to be added to that being by which it would be determined to this or that thing, just as form is determined by matter. Thus God has nothing added to his being itself: for this reason he is pure and simple being.

Likewise, although he is being alone, it does not follow that the other perfections and nobilities are lacking in him. Indeed, he has all the perfections found in all genera, for which reason he is called simply perfect, as the Philosopher and the Commentator say in Book V of the Metaphysics; but he has them in a more excellent mode than all things, because in him they are one, whereas in other things they have diversity. This is because all those perfections belong to him according to his simple being. Thus, if someone could produce the operations of all qualities through one quality, he would possess all qualities in that one quality; so God possesses all perfections in his very being.

In a second way essence is found in created intellectual substances, in which their being is other than their essence, although their essence is without matter. Hence their being is not absolute but received, and therefore limited and finite according to the capacity of the receiving nature; but their nature or quiddity is absolute, not received in some matter. Therefore it is said in the Book of Causes that intelligences are infinite below and finite above: they are finite with respect to their being, which they receive from a higher being, but they are not bounded below, because their forms are not limited to the capacity of some matter receiving them. Consequently, in such substances a multitude of individuals in one species is not found, except in the human soul because of the body to which it is united. And although its individuation depends accidentally on the body with respect to its beginning, individuated being is not acquired by it except in the body of which it is the act; nevertheless, when the body is taken away, individuation need not perish, because, since it has absolute being, from which individuated being was acquired for it by becoming the form of this body, that being always remains individuated. Hence Avicenna says that the individuation and multiplication of souls depends on the body with respect to its beginning, but not with respect to its end.

And because in these substances quiddity is not the same as being, they can therefore be ordered in a category; and for this reason genus, species, and difference are found in them, although their proper differences are hidden from us. For in sensible things the essential differences themselves are also unknown; hence they are signified through accidental differences arising from the essential ones, just as a cause is signified through its effect: thus biped is posited as the difference of human being. But the proper accidents of immaterial substances are unknown to us, and therefore their differences can be signified by us neither through themselves nor through accidental differences.

Nevertheless, one must know that genus and difference are not taken in the same way in those substances and in sensible substances. For in sensible substances genus is taken from what is material in the thing, while difference is taken from what is formal in it. Hence Avicenna says at the beginning of his Book of the Soul that form in things composed of matter and form “is its simple difference which is constituted from it”; not, however, in the sense that the form itself is the difference, but because it is the principle of the difference, as he says in the same way in his Metaphysics. Such a difference is called a simple difference because it is taken from what is a part of the thing, namely, the form. But since the quiddities of immaterial substances are simple quiddities, in them difference cannot be taken from what is a part of the quiddity, but from the whole quiddity. Therefore at the beginning of the Book of the Soul Avicenna says that “only those species whose essences are composed of matter and form have a simple difference.”

Likewise, in them genus is taken from the whole essence, but in a different way. One separate substance agrees with another in immateriality, but they differ from one another in degree of perfection according to their withdrawal from potentiality and approach to pure act. Therefore, from what follows upon them insofar as they are immaterial, genus is taken in them, such as intellectuality or something of this sort; but from what follows upon them according to their degree of perfection, difference is taken in them, although it is unknown to us. Nor need these differences be accidental, because they are according to greater and lesser perfection, which do not diversify the species. For a degree of perfection in receiving the same form does not diversify the species, as what is whiter and less white do not differ in species when participating in whiteness according to the same account; but a diverse degree of perfection in the forms or natures themselves that are participated does diversify the species, as nature proceeds by degrees from plants to animals through certain things intermediate between animals and plants, according to the Philosopher in Book VII of On Animals. Nor again is it necessary that the division of intellectual substances always be through two true differences, because it is impossible for this to occur in all things, as the Philosopher says in Book XI of On Animals.

In a third way essence is found in substances composed of matter and form. In them being is received and finite because they have being from another, and again their nature or quiddity is received in designated matter. Therefore they are finite both above and below; and in them, because of the division of designated matter, the multiplication of individuals in one species is now possible. And how essence is related to logical intentions in these things was said above.