Possibility and Existence

According to David Berlinski, Thomas Aquinas argued the universe must have begun at a finite time in the past by appealing to Diodorus’s (1st cent. B.C. Greek philosopher) view of possibility: if it is possible that something not exist, then it is certain that at some time or another it did not exist. Only that which has a necessary existence can be, and must be eternal. [1]

Aquinas argued that while our universe does exist, it does not have to exist. It is contingent, not necessary. This much seems reasonable. After all, it is possible to conceive of our universe not existing. There is nothing about the physical constituents of the universe that demands they exist. Using Diodorus’s principle, Aquinas concluded that since it is possible that our universe not exist, then it is certain that at some time in the past it did not exist.

Berlinksi thinks Aquinas’ argument commits the fallacy of composition (e.g. just because every part of an elephant is light, does not mean the elephant as a whole is light). He argues that while Diodorus’s principle might be true of things in the universe, it is not necessarily true of the universe as a whole. But I think Berlinski misses the point. The point is that only necessary things must exist eternally. Nothing else needs to, or can for that matter. Contingent things have causes, and hence beginnings.

What do you think of Aquinas’s argument, Berlinski’s criticism, or my response? I tend to think this is a decent argument for the finitude of the universe. What do you think?

[1]David Berlinski, The Devil’s Delusion: Atheism and Its Scientific Pretensions (New York: Crown Forum, 2008), 85.

Scalia Says:

March 10, 2021 at 10:13 am

Well, better late than never, I say. I think that Aquinas got most of his metaphysics from Aristotle, albeit as significantly refined by Aquinas. Recall that Aristotle sought to understand the change we observe in the world. In contrast to those who said that change is constant with nothing permanent to those who insisted that all change is illusory, things undeniably exist and whatever exists is a “substance.” A substance is that whose nature is to exist not in some subject (e.g. greenness in a leaf) or as a part of something, but what exists in itself (e.g. a dog, tree, rock). These substances arise via generation (e.g. fertilization) and demise via corruption (melting down a rubber ball to make an eraser). Thus, every substance which undergoes generation and corruption is a possible (contingent), not necessary existence (this of course addresses naturalism). And everything possible or contingent depends upon another for its existence. With that in mind, let’s look directly at Aquinas’ Third Way:

We find in nature things that are possible to be and not to be, since they are found to be generated, and to corrupt, and consequently, they are possible to be and not to be. But it is impossible for these always to exist, for that which is possible not to be at some time is not. Therefore, if everything is possible not to be, then at one time there could have been nothing in existence. Now if this were true, even now there would be nothing in existence, because that which does not exist only begins to exist by something already existing. Therefore, if at one time nothing was in existence, it would have been impossible for anything to have begun to exist; and thus even now nothing would be in existence—which is absurd.

Therefore, not all beings are merely possible, but there must exist something the existence of which is necessary. But every necessary thing either has its necessity caused by another, or not. Now it is impossible to go on to infinity in necessary things which have their necessity caused by another, as has been already proved in regard to efficient causes. Therefore we cannot but postulate the existence of some being having of itself its own necessity, and not receiving it from another, but rather causing in others their necessity. This all men speak of as God.

Against this argument, some have appealed to infinite regress (IR), and they have pointed out that even Aquinas, though affirming creatio ex nihilo as a matter of scriptural special revelation, did not deny that IR was something that could not be philosophically disproved. So, if IR cannot be disproved, it stands as a defeater to the assertion that everything being contingent results in non-existence at some past point.

The objection is mistaken for several reasons. First, Aquinas does not offer his argument in isolation from his other arguments. They all work together to illustrate what he painstakingly argues in his other works (remember that the “Summa” is a “summary” and not a full argument). Second, the causal principle (whatever is moved is moved by another) proves that even if a series is infinite, its contingency, by definition, shows its ontological dependence on an exterior cause. So, like the ray from an eternal sun, even if the ray were eternal, without the causal efficacy of the sun, the ray would not exist. The ray, by definition, is caused by the sun, so nothing which cannot account for the effect of its existence can exist without a cause whose essence is to exist. Third, Aquinas takes care to focus on generation and corruption. Those things which come to be at one time were not (again, by definition) and all possible beings inherently corrupt sooner or later. If EVERYTHING is a possible existence, then EVERYTHING has to have a beginning. However, it seems possible, at least in theory that a series of contingent things could exist in infinite temporal succession, one coming into being after another. Yet, it is possible that the myriad temporal causes and effects could (to use Aquinas’ word) result in non-existence. And since non-existence is a real possibility, then something necessary must be the cause of the contingent (since something cannot come from nothing). But even conceding IR, we have a SERIES of things which, if it is really past-infinite, has no beginning. So, at the very least, the series, or whatever grounds it, cannot be a possible being. This of course means that at least one aspect of reality is necessary, not possible.

Recall also, that Aquinas posits multiple necessary beings for he does not define necessity like some modern philosophers do. To Aquinas, a necessary substance is one that does not undergo generation and corruption in accordance with the doctrine of hylomorphism (the conjoining of form and matter). Matter always exists in some form, and the movement of matter from one form to another is an example of change, and this is what is referred to as generation and corruption. When matter takes a new form, a “new” substance is generated, and when said substance changes from one form to another, the original substance is said to be corrupted (goes out of existence). Aquinas believed that some substances do not experience generation and corruption in the hylomorphic sense and were thus a type of necessary existence (not subject to corruptible tendencies, e.g. an angel), but nonetheless grounded their “necessity” in an absolute necessity which is God. Though “necessary” substances do not experience “generation and corruption,” they, being act/potency composites, are thus dependent (via the causal principle) on something not a composite of act/potency — Pure Act, which is God. Thus, all possible existents and derivative necessary existents must be grounded in absolute necessity. And this absolute necessity is what we call God.

Without an efficient cause of an essentially ordered series of movement relative to existence, there is no effect and, hence, no existence. Thus, as you also affirm, if the parts are contingent, so is the whole. This cannot a fallacy of composition because it speaks to the intrinsic nature of the composite. Size and weight are relative, essence is not.

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June 21, 2023 at 7:53 am

One correction of Berlinski is that Aquinas did not argue that the universe began at a finite time in the past. Most certainly, that is what he believed, but Aquinas felt that it could not be demonstrated philosophically. He accepted the “finite” beginning of the universe on the basis of the special revelation of Scripture. He, nonetheless, assumed an eternal universe arguendo to prove that even an eternal universe needs its ground in God.

The possible existence in Aquinas’ argument applies to those things in the universe which obviously come into and go out of existence. Since he is assuming an eternal universe, he uses the generation and corruption of some things to show that some other things are necessary (he believed that some material things were not subject to generation and corruption) and from there, that qualified necessity is grounded in God.

Thinking to Believe