Thinking to Believe

May 17, 2024

2 Responses to “Thomas Aquinas’ Third Way: Argument from Contingency”

1. Scalia Says:

   
   May 20, 2024 at 11:04 pm

   I’ve privately expressed to Jason my disagreement with his description of the Third Way. In his defense, other Thomists have expressed similar sentiments. They seem to think that Aquinas was relying on the essence/existence distinction to illustrate a possible being. So, let’s look at the Third Way as Aquinas presented it:

   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.

   So, on Aquinas’ own terms, a possible being is one which undergoes generation and corruption, which in classical metaphysics is the acquiring and loss of substantial form via the principles of causality (the raising of potency to act). Further, Aquinas discusses possible beings in an earlier work entitled Summa Contra Gentiles. In Book I, Chapter 15, he writes:

   [2] Everything that begins to be or ceases to be does so through motion or change. Since, however, we have shown that God is absolutely immutable, He is eternal, lacking all beginning or end.

   [3] Again. Those beings alone are measured by time that are moved. For time, as is made clear in Physics IV [11], is “the number of motion.” But God, as has been proved, is absolutely without motion, and is consequently not measured by time…

   [5] We find in the world, furthermore, certain beings, those namely that are subject to generation and corruption, which can be and not-be. But what can be has a cause because, since it is equally related to two contraries, namely, being and non-being, it must be owing to some cause that being accrues to it. Now, as we have proved by the reasoning of Aristotle, one cannot proceed to infinity among causes. We must therefore posit something that is a necessary being. Every necessary being, however, either has the cause of its necessity in an outside source or, if it does not, it is necessary through itself. But one cannot proceed to infinity among necessary beings the cause of whose necessity lies in an outside source. We must therefore posit a first necessary being, which is necessary through itself. This is God, since, as we have shown, He is the first cause. God, therefore, is eternal, since whatever is necessary through itself is eternal (bold emphasis added).

   So, the argument from possibility to necessity rests on Aristotle’s causal argument, which Jason adequately describes in his podcast on the First Way (a per se or essentially ordered causal series). The concurrent causal activity of Pure Actuality is the only ground for possible and suppositionally necessary beings.

   Since possible beings are generated and corrupted (acquire and lose substantial form), then at one time they were not. But if everything were a possible existence, then nothing would exist now, given the essentially ordered causal chain which requires a ground. And since suppositionally necessary beings are only proximate efficient causes, they too must be grounded in an absolutely necessary cause, which is God. It is at the point of discussing second-order necessary beings that the essence/existence argument (On Being and Essence) is incorporated into the Third Way.

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2. Andrew Miller Says:

   
   May 21, 2024 at 5:59 pm

   If my memory is correct: I believe Norman Geisler’s “God: A Philosophical Argument from Being” elaborates and popularizes the Third Way in that manner. Geisler specifically employs the essence/existence distinction common within Thomistic metaphysics.

   Although we have labeled this Thomistic argument as “Argument from Contingency.” To avoid further confusion with Leibnizian and PSR Contingency Arguments, I have opted to call the Third Way ‘Argument from Being’ since it accurately alludes to the essentiality of the Thomistic essence/existence distinction. My most recent blog post covers that Geisler’s argument minimally.

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