|||Aquinas, Thomas and Ralph McInerny. On Being and Essence. Thomas Aquinas: Selected Writings. London; Penguin Books, 1998.|||
Although they (intelligences) are forms alone without any matter, such substances are not utterly simple nor pure act. They have a tinge of potentiality, which is clear from this–that whatever does not enter into the understanding of an essence or quiddity comes to it from without and is composed with the essence. No essence can be understood without the things that are parts of the essence. But every essence or quiddity can be understood without its existence being understood: for I can understand what a man or phoenix is and yet not know whether they exist in reality. Therefore, it is clear that to exist is other than the essence or quiddity. Unless of course there is something whose quiddity is its very existence. Such a thing is first and one, because it is impossible for there to be a multiplication of anything except by the addition of some difference, as the nature of genus is multiplied into species; either because form is received in diverse matters, as the nature of species is multiplied in diverse individuals, or because one is absolute and the other received in something, as if there were some separated heat it would be other than a non-separated heat by its very separation. If, however, there is given a thing which is existence alone, subsisting existence itself, this existence would not receive the addition of a difference, since it would not then be existence alone but existence along with some form. Much less would it receive the addition of matter, since then it would not be subsistent but material. Consequently, a thing which is its own existence can only be one, and it must be said that in every other thing its existence is one thing and its quiddity or nature or form other. In intelligences existence must be outside form, and that is why it is said that an intelligence is form and existence. p. 42
Here, in On Being and Essence, we find the heart of Thomas Aquinas’ argument for the distinction between essence and existence. Some preliminary remarks are in order. First, one of Aquinas’ most important axioms, on which he builds, is that act is not self-limiting. At the beginning of the quote, Aquinas distinguishes intelligences (angels) from something “utterly simple” and “pure act.” Something is said to be simple in two ways: (1) that it is not composed of matter and form, or (2) that there is no composition whatsoever (“utterly simple” or “pure act”).
Using the angels as an example can lead us to be skeptical about the philosophical strength of this paragraph. However, Aquinas presents a second example later. Let us focus on this example, heat. Along Platonic lines, let us suppose that there is a separate form that exists which is the perfection of heat. When we find heat in a material object, the heat is limited by the matter of the object. The form of heat (“heatness”), though, is completely separate from matter. It is not received in something that limits it. If there were no matter to limit heatness, then would it not be completely unlimited? Just as we saw in the Timaeus, it is impossible for there to be more than one purely infinite entity. All of the forms, if they have a separate existence, must have some potentiality. But potentiality involves composition.
Now we must look for the principle with which the form is composed in order to have existence. Where does it come from? This principle cannot come from the essence itself as a part, because the parts of the essence make up the essence. If a part of the essence of heat were responsible for heatness’s existence, then the intelligibility of heat would change when consideration changes from the form alone to the consideration of it as existing in something. However, the intelligibility of heatness has not changed. Therefore, the principle with which heatness is composed comes from outside its essence. The essence of heatness combines with the principle of existence in order for heatness (as the form of heat) to exist. The way that Plato treats the forms is very similar to the way that Aquinas treats the angels. Even if they exist without matter, they must be limited in some way.
Why has Aquinas decided to examine such forms that do not depend on matter? He does so because it is difficult for us to reach the intellectual heights of contemplating being as being. That is to say, in our imaginations, we can move up Porphyry’s tree to wider concepts. What is left, though, if we remove any properties we find in beings and try to think of being without any particular essence? As we saw for Duns Scotus, if you move up the tree to the 10 genera, and then to the genus above them, you reach finite being. Finally, above that genus is the ultimate genus, being. There is no difference between moving up the tree from rational animal to animal and moving from substance to finite being. When Aquinas, following Aristotle, says that being is not a genus, he has a different understanding of what happens when the intellect moves from consideration of substance to being as being. We must take a moment to backtrack and examine more closely the terms that Aquinas uses in the quote above. What are rendered as “to exist” and “existence” above are in Latin represented by esse (“to be”). When Aquinas speaks of “being as being”, in Latin he writes, “ens qua ens” (ens is expressed as “that which is”). It is difficult to render the difference between these two terms in English. Another attempt, by Dr. Walter Redmond, renders ens as “being” and esse as “be-ing”. The difference is subtle, and does capture some of the difference in meaning. It does not, however, quite capture the difference between the uses of the two terms. In his commentary on the De Hebdomadibus of Boethius, Aquinas says, “First he says that to be (esse) and that which is (ens) are different. This difference is not now to be referred to things, of which he does not yet speak, but to the notions or intentions themselves. For we mean one thing when we say ‘to be’ and another when we say ‘that which is’, just as we signify one thing by ‘to run’ and another by ‘runner’. For ‘to run’ and ‘to be’ (esse) are signified in the abstract, like ‘whiteness’, but ‘what is’, that is ‘being’ (ens) and ‘runner’, are signified in the concrete, like white.”1 Just as the action of running must ultimately be in something, ens is the principle of existence in something. Esse, however, expresses existence as a principle, an action, and can be conceived separately from a something, just as I know what “to run” is even without picturing someone running. Let us return now to our discussion of ens as a genus. If Duns Scotus moves up the tree, he eventually reaches the notion of ens. Any particular essence has been removed, and now you have an empty thing that has existence and nothing else, nothing particular to anything with an essence. That is a tempting representation, and one we are probably better equipped to do today than Aquinas was back then (thanks to Descartes). You start with ens; then the essence is added; and then you have an individual. However, Aquinas has something else in mind. Using material beings as the example clouds our approach, because in addition to the principles of essence and existence, we have to deal with matter and form. That is why he has moved to a higher level of being. It is easier to see what goes on when we remove matter and form from view. Even if the forms existed separately from matter, there must be a principle outside of the essence that caused them to exist. Being, the principle of existence, cannot be in Porphyry’s tree after all. It is a principle completely separate from the tree of essences.
We have an interesting turn of events. In corporeal things, we think of the form as the actualizing principle and the matter as the receiving principle that limits the form. However, there is now a double potency. The essence is in potency until it receives the principle of existence (esse). Just as we would not say that animal individuates rational animal into an individual man, it would be wrong to say that rational animal is individuated into a man by ens (conceived as a genus). Esse comes to the essence from outside and creates an individual. It is also improper to think of esse as having its own parallel tree (even thinking of esse in itself as divided between infinite and finite, as Duns Scotus did). Esse individuates but is limited by the essence of the receiver, just as matter limits the form and a subject limits an accident. How all of that works (Aquinas’ theory of participation) will have to come in a different article. However, the fact that esse cannot be divided like a genus and species is what Aquinas addresses when he says that being is predicated of things analogically (analogically both between things in different categories and between two things of the same species). We also see why Aquinas states that each angel is its own species, since there is no matter to distinguish one from another.
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Ibid., 147. ↩