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  • A Restatement of the Fourth Thomistic-Aristotelian Way to Prove the Existence of God
  • Carlos A. Casanova

AMONG ST. THOMAS AQUINAS'S five ways to prove the existence of God, the two strongest are the one based on the contingency and necessity of beings and the one based on the degrees of perfection. The latter has been subject to harsh attacks recently. The goals of my present effort are to elucidate and assess this proof, with an eye toward demonstrating its relevance and forcefulness in our current culture.1 Ángel Luis González has made an interesting observation which has served as a guide in the writing of this paper. Today, in the consideration of Thomas's "Five Ways,"

the predominance of historical studies over and above properly philosophical studies is manifest.… [But,] what really matters is to know whether the existence of God can be rationally proved; what is capital is to know whether God exists and whether this existence can be rationally demonstrated.2

This paper will advance only one argument, which is an expanded version of that found in the Prima pars of the Summa theologiae, question 2, article 3 (which is fuller than the version [End Page 361] contained in the Summa contra gentiles I, c. 13). It is essentially the same as that given by Aristotle in book a, section 1 of the Metaphysics, enriched with his investigations in books Γ, Θ, and Λ. My understanding of the argument differs from that presented by many Thomists, although some of those presentations, especially that of Ángel Luis González, are effective in proving the existence of God. I argue that the Aristotelian way differs from that of González and has much greater persuasive strength and is much more understandable for persons not deeply instructed in Thomistic metaphysics. To highlight the strength of this argument, I will note some important observations by Friedrich Nietzsche. Nietzsche is the staunchest and most articulate enemy of theism. He has persuaded even an important German Thomist that the principles from which the proofs about God's existence proceed are accepted through an act not of the intellect but of the will, that is, an act of choice.3 For this reason, to show that Nietzsche himself perceived the commanding force of the argument seems important in the contemporary context.

I. The Argument in the Summa theologiae and Its Source in Aristotle's Metaphysics

The text of the argument from the Summa theologiae is as follows:

The fourth way is taken from the gradation to be found in things. Among beings there are some more and some less good, true, noble and the like. But "more" and "less" are predicated of different things, according as they approach in their different ways something which is the maximum, as a thing is said to be hotter according as it more nearly approaches that which is hottest; so that there is something which is truest, something best, something noblest and, consequently, something which is uttermost being; for those things that are greatest in truth are greatest in being, as it is written in Metaph. [End Page 362] ii. Now the maximum in any genus is the cause of all in that genus; as fire, which is the maximum heat, is the cause of all hot things. Therefore there must also be something which is to all beings the cause of their being, goodness, and every other perfection; and this we call God.4

In commenting on this passage I will focus on the degrees of truth (i.e., intelligibility), which is how the original Aristotelian argument is formulated. Once we show that it proves the existence of a highest truth, which is the ultimate cause of the lower degrees, the argument can be applied to the other transcendental perfections.5

A) The Degrees of Perfection and Their Connection to a Maximum Degree

I must begin by clearing up a confusion. Regarding this passage, Etienne Gilson said the following: [End Page 363]

The main reason for the disagreement [among those who interpret these lines] lies in the fact that, although [it is evident that] in both Summae the presentation of the...


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