Reader Ante asks the following question in the comments of my response to his previous question:

The issue I have is with regards to God’s necessary existence. Since God’s essence and existence are identical, He exists necessarily. But the same thing could be said of matter as well, as it seems to me. Why could it not be the case that some fundamental layer of physical reality necessarily exists aka that it cannot fail to exist? Suppose that we are dealing with some form of “atomism”. How do we know that some kind of physical particles or fields don’t have necessary existence? Existence could be a PART of particles/fields or some other kind of fundamental physical reality. Then, what it means to be a particle/field ENTAILS, among other things, that this particle/field EXISTS.

In fact, there are three related questions in here. Here we’ll try to disentangle them from one another, and give a brief answer to each.

Q1. Does matter have necessary existence?

Without trying to sound facetious, it depends on what you mean by “matter,” “necessary,” and “existence.”

Starting with matter, there are at least three senses that it can have. In contemporary usage, matter refers to the “stuff” that underlies physical reality — atoms, electrons, quarks, bosons, and so on. Then there is matter in the Aristotelian sense, which comes in two varieties, namely primary and secondary matter. Unlike the contemporary “physical” matter, the Aristotelian “metaphysical” matter is never a thing of itself, but is always a constitutive principle of things. It composes with form to, well, form composite things, such as animals, people, actions, and aggregates.

In general, this composition works as follows: matter is a substratum that of itself is indeterminate between various alternatives, while form is the determination of that substratum to one of those alternatives. So, the matter and form of a thing do not exist separately from one another, but each exists indirectly through the existence of the thing they compose. The form and matter of a human exist where I am, for example, because I am a human composed of form and matter. When a thing changes it switches one form for another, but retains the same underlying matter. When a thing changes without being destroyed, like me standing up or changing clothes, then we’re talking about secondary matter composed with accidental form. But when the change brings about the destruction of one thing and the beginning of another thing, as when I die and become a corpse, then we’re talking about primary matter and substantial form. Primary matter is therefore more fundamental than secondary matter, and in some sense it persists across all change, even though whenever it exists it does so indirectly through the things it composes.

With necessary existence there is also a distinction between contemporary usage and classical usage. In contemporary metaphysics, “necessary” and “contingent” are cashed out in terms of possible worlds: a thing has necessary existence if it exists in every possible world, and has contingent existence if it fails to exist in some possible worlds. Since possible worlds capture what could have been the case, a thing exists necessarily if it could not have been the case that it failed to exist, while it exists contingently if it could have been the case that it failed to exist.

When Aquinas refers to things as necessary and contingent, however, he has something quite different in mind. He is not talking about whether things may or may not exist in other possible worlds, but whether things are corruptible or not — whether they go in and out of existence — in this possible world. For him, the corruptibility of something is a consequence of its nature: material things are made up of these two principles which need not be composed (form and matter), and therefore they are corruptible. Angels and God, on the other hand, are incorruptible. For the sake of clarity, then, we will refer to the necessary existence of Aquinas as “incorruptibility” and the necessary existence of contemporary metaphysics as “metaphysical necessity.”

In order to understand how a Thomist would approach the question of metaphysical necessity, we can compare it to a position defended by some in contemporary metaphysics, called “modal essentialism.” Broadly speaking, modal essentialists seek to analyze the notion of “essence” in terms of facts about possible worlds: the essence of a thing is the collection of its essential properties, and a property of a thing is essential if that thing has that property in every possible world it exists. Thomists, by contrast, hold to a position that has been called “real essentialism,” where essences are fundamental to things, and the truths about possible worlds are grounded in them rather than the other way around.¹ Thus, from our point of view, modal essentialism gets things backwards.

An important consequence of real essentialism is that it allows essences to govern whether something is metaphysically necessary or not. For the Thomist, the essence of every thing apart from God is really distinct from its existence, with the former being a potential of some kind and the latter being its continued actualization. Now, every potential depends on another actuality for its continued actualization, and every chain of actualized potentials eventually leads back to God. Furthermore, since God is a free agent, it is metaphysically contingent whether he chooses to actualize any potentials at all, and therefore it is a metaphysically contingent fact that anything other than himself exists from moment to moment. God is the only exemption from this, because he does not exist through the actualization of a potential — he is pure actuality, his essence is his existence. Thus, God is metaphysically necessary while everything else is metaphysically contingent.

Returning to the two kinds of matter, every material thing exists through the actualization of a potential. Since contemporary matter is a material thing it is therefore metaphysically contingent along with every other material thing. Aristotelian matter, as we have said, exists at any moment indirectly through the existence of the material thing it makes up, and therefore will also be metaphysically contingent.

But they are not in the same boat when it comes to corruptibility. Contemporary matter is corruptible, since like any material thing it comes in and goes out of existence. Likewise, Aristotelian secondary matter comes in and goes out of existence along with the substances to which it belongs. But since Aristotelian primary matter persists through all generation and corruption, it is in some sense never generated or corrupted itself, and is therefore in that sense incorruptible. Of course, it is incorruptible in the thinnest sense. Even though it always exists, at any given moment it only exists indirectly through the substances it composes. And so, it would go out of existence the moment God stopped sustaining all material things in existence.

Indeed, primary matter might be the first incorruptible thing arrived at in Aquinas’s Third Way. At a crucial point in the argument, which has generated much discussion, he says, “if everything is corruptible, then at one time there could have been nothing in existence.” On the face of it, this sounds like he’s committing the quantifier shift fallacy. And this might be the case if he was only quantifying over substances, but if he was quantifying over substances and their principles then this shift is quite reasonable. If primary matter is also corruptible, then it also wouldn’t have existed at some time in the past. But since, for Aquinas, generation depends on pre-existing matter, it would follow that nothing could have subsequently been generated, which is contrary to experience. This leads him to posit the first incorruptible thing in his chain of incorruptible things, namely primary matter, from which point he traces the chain all the way back to God, the only incorruptible thing that is also metaphysically necessary.

So, does matter have necessary existence? In some sense yes, but mostly no:

	Contemporary matter	Primary matter	Secondary matter
Metaphysically necessary	No	No	No
Incorruptible	No	Yes	No

Q2. What if atomism were true?

Would our answer change if some form of atomism were true? In this case, there would presumably be a bunch of fundamental physical things called “atoms,” which would not come in or go out of existence. This would certainly make them incorruptible, like Aristotelian primary matter, but would it make them metaphysically necessary?

It’s tempting to reach for our earlier answer about primary matter and apply it to these atoms, but that would be a mistake. For that answer, it was crucial that primary matter is a principle of things rather than a thing of itself. Because of this, its existence at any moment is in some sense parasitic on the composite thing to which it belongs, and if God simply stopped sustaining all composite things in existence, then primary matter would disappear along with them. By contrast, these atoms are not principles, but things in their own right, so the same line of argumentation won’t work.

A better analogy would be the angels. They are incorruptible, since they are not made out of matter at all, but their essence is nevertheless really distinct from their existence, which means they exist through the continued actualization of a potential, and therefore depend on God for their continued existence. So, what reason could there be for thinking that these atoms would need to likewise exist through the continued actualization of potentials?

For one thing, they are material, and therefore exist through the actualization of potentials of primary matter like any other material thing. What makes them different from other material things is not that this doesn’t apply to them, but rather that this applies to them without them being generated or corrupted.

For another thing, we saw earlier that anything whose essence is not identical to its existence is metaphysically contingent, and there can be only one being whose essence is identical with their existence. I covered this in a previous post on the real distinction, but briefly: existence unifies all existing things as existing, whereas essence diversifies us within this unity by limiting that existence in various ways. One thing is distinct from another by virtue of being limited in a way that the other is not. Material things with the same common essence are diversified by differing determinate dimensions, which limit us to different places and times; created immaterial substances (angels) are diversified simply by their individual essences, so that there are no two angels have their existence limited in a common way; and God is that existence which is not limited in any way by his essence, since they are identical. Since diversity occurs through limitation, and since a thing whose essence is identical to its existence is not limited, there cannot be a diversity of such things.

Q3. Could existence be part of an essence without being identical to it?

But what if the existence of these atoms was really distinct but not wholly distinct from their essences? That is, why couldn’t their existence be a proper part of their essence?

Let’s start by considering some things which are parts of essences: substantial form and primary matter. When we first learn about form and matter, they are said to correspond to actuality and potentiality — the indeterminacy of matter corresponds to its potential for being in different ways, and the determination of this matter by the form is an actualization of one of those potentials. But things get a little confusing, later, when we then learn that both form and matter are parts of an essence, and that essence is a sort of potentiality for existence. How is it possible that form is an actuality but part of a potentiality?

Fundamentally, this boils down to the fact that the form-matter distinction is orthogonal to the essence-existence distinction. In a composite being, there are these two overlapping real distinctions, each of which focuses on the actualization of a potential in different but complementary ways. The form-matter distinction captures what obtains when a material thing exists, while the essence-existence distinction captures whether this obtains in reality. Form accounts for the unity a material thing has with all other material things of the same kind, and matter distinguishes this instance of the kind from that instance of the kind. Existence accounts for the unity a thing has with all existing things, and essence distinguishes this existing thing from that existing thing.

To put this in more concrete terms, we can compare me, Sherlock Holmes, and the tree outside my house. Many people don’t know this about me, but I’m a composite of form and matter.² Likewise, the tree is a composite of form and matter, although my form makes me a human while the tree’s form makes it a tree. Sherlock Holmes is also a composite of form and matter, since this is part of being a human, and he would have the same sort of form that I do. Now, in one sense I am more similar to Sherlock Holmes than to the tree, but in another sense I am more similar to the tree than to Sherlock Holmes. The difference lies in whether we consider things in terms of their form and matter, or in terms of their essence and existence: I am similar to Sherlock Holmes in virtue of our shared form which the tree does not have, and I am similar to the tree in virtue of our shared existence which Sherlock Holmes does not have.

The Sherlock Holmes case also lets us see how the actuality of form can be part of the potentiality of essence. Consider this question: does Sherlock Holmes’s substantial form actualize a potential in his primary matter? Well, in one sense of course it does, for if it didn’t then he wouldn’t be a human capable of sleuthing around London. But in another sense of course it does not, for if it did then he would be a real human rather than a fictional character. It’s the difference between these two senses that is captured by the actualization of an essence by its existence — form is always the actualization a potential of matter, but it’s when this actualization obtains in reality that this corresponds to the actualization of something’s essence by its existence.

Since the actualization of matter by form is what constitutes the existence of a composite thing, and since this actualization is contained in the essence of a thing, we could in some sense say that the “existence” of a thing is contained in its essence. But, as we’ve just seen, this will not help in the present case, because this doesn’t determine one way or the other whether the thing’s existence obtains in reality. The core of the problem is that an essence, of itself, is indifferent to whether it obtains in reality or not, which is why we can talk of the essence of Sherlock Holmes without falling into incoherence. This is the indifference that I’ve recently noted belongs to all potentials, and it is on account of this that we say essence is a potential.

But why couldn’t the existence which is the actualization of the essence (and accounts for it obtaining in reality) be a proper part of that essence? Because this would entail that the essence is capable of having multiple simultaneous existences, which is absurd. To see this, let A be the part of the essence which is also the thing’s existence and let B be the other part (or the collection of other parts). From this it follows that A is an actuality since existence is a sort of actuality, and B is a potentiality since it is the part of the thing’s essence that is not its existence. In order for B to exist, then, it would need to be actualized. The resulting actuality, call it A2, would need to be separate from A. Why? Because, as we’ve seen in our above discussions on the essence-existence and form-matter distinctions, actualities are distinguished from one another by reference to the potentials they are the actualizations of (or, in the special case, because one is an actualized potential and the other is a pure actuality). So, since A is not the actualization of B but A2 is, it follows that A and A2 are distinct actualities. But since A is stipulated to be the existence of the thing, and since A2 is the actualization of the essence of the thing, it follows that A and A2 are distinct existences of the same thing.

In fact, a parallel argument could be raised against any proposal that seeks to divide an essence into parts, whether they all be actualities, all potentials, or a mixture of the two. An essence must be a single potential or actuality. It might have parts in the sense we were considering earlier, but these are not parts in the sense we’re talking about now. That is, an essence can have parts in the sense that it is the potential for the existence of a composite thing, not in the sense that it itself is a composite thing.

Conclusion and further reading

In the course of these answers we’ve had to go through some pretty heavy Aristotelian metaphysics, hitting all the important distinctions and clarifying them as we go. Of course so much more can and has been said about each one, but I can’t hope to cover all of that in one blog post. So, Ante, I hope what I’ve said has at least helped you along the way a bit.

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1. Non-Thomist contemporary philosophers have also taken exception to the modal essentialist proposal. See, for instance, Kit Fine’s “Essence and Modality.” For longer discussions on these issues, see Ross Inman’s Substantial Priority and David Oderberg’s Real Essentialism.↩
2. It’s funny because it’s true: the vast majority of the human population is not interested in philosophy and would have no idea what it even means to be a form-matter composite. Nor, as my housemate notes, does the vast majority of the human race know me at all.↩