Chapter 5 — How essence is found in various kinds of things

Having treated these matters, we can see clearly how essence is found in various kinds of things. There are thus three ways in which substances may have an essence. First, surely, is the way God has his essence, which is his very existence itself, and so we find certain philosophers saying that God does not have a quiddity or essence because his essence is not other than his existence. From this it follows that he is not in any genus, for everything that is in a genus has a quiddity beyond its existence, since the quiddity or nature of the genus or species is not in the order of nature distinguished in the things of which it is the genus or species, but the existence is diverse in diverse things.

Even though we say that God is existence alone, we should not fall into the error of those who said that God is that universal existence by which everything formally exists. The existence which is God is of such a kind that no addition can be made to it, whence through its purity it is distinct from every other existence; for this reason a comment on the Liber de causis 9 says that the individuation of the first cause, which is being alone, is through its pure goodness. But common existence, just as it does not include in its concept any addition, does not exclude any addition in its concept; for, if such existence did in its concept exclude any addition, nothing could be understood to exist in which there was added something beyond existence.

Similarly, although God is existence alone, the remaining perfections and nobilities are not lacking in him. On the contrary, he has all the perfections that exist in every genus, and for this reason he is called perfect without qualification, as the Philosopher, in Metaphysics 5.16, (Aristotle, Metaphysics, 1021b30–33.) and the Commentator, in Metaphysics 5, com. 21, each say. But God has these perfections in a more excellent way than all other things have them, because in him they are one, while in other things they are diverse. And this is because all these perfections pertain to God according to his simple existence, just as, if someone through one quality could effect the operations of all qualities, such a person would have in that one quality all the qualities, so too does God in his very existence have all the perfections.

In a second way, essence is found in created intellectual substances in which existence is other than essence, although in these substances the essence is without matter. Hence, their existence is not absolute but received, and so finite and limited by the capacity of the receiving nature; but their nature or quiddity is absolute and is not received in any matter. Thus, it says in the Liber de causis 16 that intelligences are infinite with respect to what is inferior to them and finite with respect to what is superior to them: they are finite with respect to their existence, which they receive from something superior, although they are not rendered finite with respect to what is inferior to them because their forms are not limited to the capacity of some matter receiving them.

And thus among such substances we do not find a multitude of individuals in one species, as was said above, except in the case of the human soul, and there we do find a multitude of individuals in one species because of the body to which the soul is united. Now, the individuation of the soul depends on the body for the occasion of its inception, for the soul does not acquire for itself individual existence unless in the body of which it is the act. But nevertheless, if we remove the body, the individuation does not perish; rather, its existence remains individuated because, since the soul was made the form of a particular body, it acquired individuated existence and so has absolute existence. And thus Avicenna says (de Anima 5.3) that the individuation of souls and their multiplication depend on the body for their beginning but not for their end.

Since in these substances the quiddity is not the same as existence, these substances can be ordered in the categories, and for this reason we find genera, species, and differences among these things, although their proper differences are hidden from us. Even in sensible things, essential differences are unknown to us, and so they are signified through accidental differences that arise from the essential ones, just as a cause is signified through its effect. We take bipedality, for example, as the difference of man. The proper accidents of immaterial substances, however, are also unknown to us, and thus we can signify their differences neither essentially nor through their accidental differences.

We should note, though, that the genus and difference in immaterial substances are not taken in the same way as in sensible substances, for in sensible substances the genus is taken from that which is material in the thing, while the difference is taken from that which is formal in the thing. Hence, Avicenna says in his book de Anima 1.1 that, in things composed of form and matter, the form is its simple difference because the thing is constituted from it; not, however, because the form is the difference but rather because it is the principle of the difference, as Avicenna himself says in his Metaphysics 5.6. Further, this difference is called a simple difference because it is taken from that which is a part of the quiddity of the thing: namely, from the form. But since immaterial substances are simple quiddities, in such substances the difference cannot be taken from that which is a part of the quiddity but only from the whole quiddity, and so in de Anima 1.1, Avicenna says that substances have no simple difference except for those species of which the essences are composed of matter and form.

Similarly, in immaterial things the genus is taken from the whole essence, though not in the same way as the difference is. Separated substance are alike with respect to their immateriality, but they differ one from another with respect to their grade of perfection according to how far each recedes from potentiality and approaches pure act. And so, in such substances, the genus is taken from that which arises in these substances insofar as they are immaterial, as intellectuality and such things; the difference, however, is taken from that which arises in these substances from their grade of perfection, although these differences are unknown to us. Nor are these differences accidental because they arise from greater and lesser perfection, which do not diversify the species. For, while the grade of perfection in receiving the same form does not diversify the species (as whiter and less white in participating in whiteness of the same type), nevertheless, a different grade of perfection in these participated forms or natures does diversify the species, just as nature proceeds by grades from plants to animals through those things that are median between plants and animals, as the Philosopher says in de Historia animalium 8.1. (Aristotle, de Historia animalium, 588b4–12.) Nor is it necessary that the division of intellectual substances always be made through two true differences, for it is impossible that this happen in all cases, as the Philosopher says in de Partibus animalium 1.2. (Aristotle, de Partibus animalium, 642b5–7.)

In a third way, essence is found in substances composed of matter and form, in which existence is both received and limited because such substances have existence from another, and again because the nature or quiddity of such substances is received in signate matter.

And thus such substances are finite both with respect to what is superior to them and with respect to what is inferior to them, and among such substances, because of the division of signate matter, there can be a multiplication of individuals in one species. Finally, we explained above the ways in which essence in such substances is related to the logical intentions.