Third Way


Notes:

A. Objection: Aquinas commits the Birthday Fallacy: since every possible being at some time does not exist, there is some one time when every (and all) possible being does not exist. Aquinas does not consider that an eternal universe satisfies Principle of Sufficient Reason (PSR) (1) [every possible being has its own particular cause(s)] but the Universe as a whole does not require a temporal beginning (e.g., the Big Bang or some prior beginning). The temporal succession of possible beings could have been going on forever, with each thing caused, but no cause of the whole temporally eternal series.

Reply: An eternal universe would be a Necessary Being, which is all that is claimed. For more, see my paper “The Alleged Birthday Fallacy in Aquinas’s Third Way.

B. An Infinite Regress in simultaneously acting caused causes is impossible (see First Way and Second Way).

C. Objection (J.L. Mackie): A Brute Fact might not exist (it is not Necessary (2) (i.e., self-necessary)) but it does without any cause. The Universe has no cause. It just is.

Reply: This is mere irrationality. The only time this concept of “Brute Fact” is ever invoked is when one declares (without any evidence) that the Universe does not need or have an explanation. It is never invoked when people encounter other contingent things or anomalous events, such as fast blue optical transients, fast radio bursts or transient lunar phenomenon or any current astronomical mystery, not to mention those in other fields of inquiry nor the myriad phenomena the explanations for which constitute the whole of science. To seek and to expect there to be explanations is just what it means to be rational (or an essential fundamental part of it), even if the explanations are not yet known or understood. If the objector were to invoke “Brute Facts” with any consistency, he/she would completely undermine science, and indeed, their own day-to-day living. The “Brute Fact” alternative to seeking an explanation for the Universe should not be taken seriously.

D. Objection: The Universe is the Self-Necessary Being.

E.  Option 1: The Self-Necessary Universe is comprised only of possible beings.

Reply: The Universe would then be more necessary than the things of which it is exclusively comprised, as though a wall comprised of only red bricks were not red. This is irrationally false.

F.  Option 2: The Self-Necessary Universe is comprised of only necessary beings; there are no possible beings. Mass/energy (or whatever underlies them) is what exists in the primary sense, and it has always existed. Everything composed of it (protons, atoms, planets, cells, animals, you and I) exist in a secondary sense, as an arrangement or state of this more basic (and more real) stuff. The secondary arrangements of mass/energy (or whatever underlies them) come and go, but the substrate (and so the Universe) cannot not exist.

Reply: This denies the first premise of the proof with which we started: some of the real things that exist are possible beings. For more on the self-contradicting nature of the scientific materialism underlying this objection, see the blog post Scientific Materialism Is No Alternative . . .

G. Aquinas relies on his Christian faith to identify the First Necessary Being as God. See the essay “This everyone calls God.


Text and Translation

Tertia via est sumpta ex possibili et necessario, quae talis est.

The third way is taken from the possible and the necessary, and is thus.

Invenimus enim in rebus quaedam quae sunt possibilia esse et non esse, cum quaedam inveniantur generari et corrumpi, et per consequens possibilia esse et non esse.

I. We find among (real) things some that are possible to be and not to be,

A. since they are found to be generated and corrupted,

B. and consequently, (they are) able to be and not to be.

Impossibile est autem omnia quae sunt, talia esse, quia quod possibile est non esse, quandoque non est.

II. But it is impossible for all the things-that-are to be like this

A. for what is possible not to be, at some time does not exist.

[English Dominican Fathers read the text as Impossibile est autem omnia quae sunt talia semper esse, quia quod possibile est non esse, quandoque non est. But it is impossible for these (lit., all which are such) always to exist, for that which is possible not to be at some time is not.]

Si igitur omnia sunt possibilia non esse, aliquando nihil fuit in rebus.

B. If, then, all things are possible not to be, at some time there was (would have been) nothing real.

Sed si hoc est verum, etiam nunc nihil esset, quia quod non est, non incipit esse nisi per aliquid quod est;

C. But if this were true, (then) even now there would be nothing, because

 i. what does not exist, does not begin to exist, except through something that does exist.

si igitur nihil fuit ens, impossibile fuit quod aliquid inciperet esse, et sic modo nihil esset, quod patet esse falsum.

ii. If therefore there (ever) was nothing existing, it would have been impossible that something (anything) would begin to be,

iii. and in this way, there would (now) exist nothing.

iv. This is clearly false.

Non ergo omnia entia sunt possibilia, sed oportet aliquid esse necessarium in rebus.

III. Therefore not all beings are (merely) possible, but there must be something real which is necessary.

Omne autem necessarium vel habet causam suae necessitatis aliunde, vel non habet.

IV. But every necessary thing either has a cause of its necessity from another, or it does not have (such a cause).

Non est autem possibile quod procedatur in infinitum in necessariis quae habent causam suae necessitatis, sicut nec in causis efficientibus, ut probatum est.

V. It is not possible that one should proceed to infinity in necessary things which have a cause of their necessity, just as neither (was it possible) in efficient causes, as has been proved.

Ergo necesse est ponere aliquid quod sit per se necessarium, non habens causam necessitatis aliunde, sed quod est causa necessitatis aliis, quod omnes dicunt Deum.

V. Therefore it is necessary to posit something

A. which is necessary in/through itself,

B. not having a cause of its necessity from another,

C. but which is the cause of the necessity of other things,

VI. which everyone calls God.


Tertia via est sumpta ex possibili et necessario, quae talis est. Invenimus enim in rebus quaedam quae sunt possibilia esse et non esse, cum quaedam inveniantur generari et corrumpi, et per consequens possibilia esse et non esse. Impossibile est autem omnia quae sunt, talia esse, quia quod possibile est non esse, quandoque non est. Si igitur omnia sunt possibilia non esse, aliquando nihil fuit in rebus. Sed si hoc est verum, etiam nunc nihil esset, quia quod non est, non incipit esse nisi per aliquid quod est; si igitur nihil fuit ens, impossibile fuit quod aliquid inciperet esse, et sic modo nihil esset, quod patet esse falsum. Non ergo omnia entia sunt possibilia, sed oportet aliquid esse necessarium in rebus. Omne autem necessarium vel habet causam suae necessitatis aliunde, vel non habet. Non est autem possibile quod procedatur in infinitum in necessariis quae habent causam suae necessitatis, sicut nec in causis efficientibus, ut probatum est. Ergo necesse est ponere aliquid quod sit per se necessarium, non habens causam necessitatis aliunde, sed quod est causa necessitatis aliis, quod omnes dicunt Deum.

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2 thoughts on “Third Way

  1. Invenimus enim in rebus quaedam quae sunt possibilia esse et non esse, cum quaedam inveniantur generari et corrumpi, et per consequens possibilia esse et non esse.

    I. We find among (real) things some that are possible to be and not to be,

    A. since they are found to be generated (come into existence) and corrupted (and cease to exist)

    B. and consequently, (they are) able to be and not to be.

    In this first sentence of the actual proof, St. Thomas explains what he is taking as the focus or perspective on sensible reality from which he will conclude that God exists. That is, he is explaining what he means by the possible and the necessary (possibili et necessario), and he starts, as I think he would say we must, with the possible. In short, as he will say anon, a thing is possible if at some time it does not exist. So, he is talking about real or natural possibility, not logical possibility and necessity.

    Aquinas is starting with a perfectly obvious observation: there are possible things, things which exist and are real; they are able to be (because they do), but more to the point, they are able not to be. We know they have this possibility of not being since at some time they do not, in fact, exist, and we know this because they came into being, and have (or will) go out of existence.

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