Does Aquinas Limit Natural Theology?

Recently, Dr. Owen Anderson, professor of philosophy and religious studies at Arizona State University, stated in his blog that Aquinas limits natural theology because Aquinas, “does not think we can use reason to show that the universe had a beginning.”

In his blog post, Anderson states that Aristotle defined the Universe as eternal and says that Aquinas adopts this error. He explains,

The essence of any argument to show the universe had a beginning will rely on the truth that what is eternal is unchangeable, and what is changeable is with a beginning. [A]nd so when the Greek Dualist says to us that the universe also had no beginning, they are changing who God is from ‘God is the creator that gives all else existence’ to ‘God is one of two things that have no beginning.’

Anderson continues, “I believe this mistake is due to a failure in Aristotle that Aquinas uncritically absorbs.”

Anderson correctly interprets Aristotle as believing the Universe to be eternal. Thomist philosopher, Étienne Gilson writes in his book “God and Philosophy” that the “world of Aristotle is there, as something that has always been and always will be. It is an eternally necessary and a necessarily eternal world.”

Anderson does say of Aquinas that he “believes that the universe had a beginning but only because scripture says that.”

He quotes Aquinas as saying, “By faith alone do we hold, and by no demonstration can it be proved that the world did not always exist” (Q46A2).

So Aquinas’ error, according to Anderson, is that Aquinas says we can only know God as Creator by Scripture, but natural theology must show by reason that the Universe has a beginning and that God is the Creator.

He says that Aquinas is more in line with fideistic presuppositionalists—that is to say the belief that we must start with God—rather than rational presuppositionalists—the view that says we must start with reason to know anything at all.

But, does Aquinas “absorb” Aristotle’s philosophy uncritically?

First, it is true that Aquinas is indebted to Aristotle for his metaphysical system; however, Aquinas does not adopt Aristotle’s natural theology uncritically.

Certainly, Aristotle’s understanding of God needed some… revision, to say the least. In his book “God and Philosophy” Gilson says, “Aristotle was positing his first self-thinking Thought as the supreme being, he certainly conceived it as a pure Act and as an infinitely powerful energy; still, his god was but the pure Act of a Thought,” he continues, “Because the supreme Thought of Aristotle was not ‘He who is,’ it could not give existence: hence the world of Aristotle was not a created world. Because the supreme thought of Aristotle was not the pure Act of existing, its self-knowledge did not entail the knowledge of all being, both actual and possible: the god of Aristotle was not a providence; he did not even know a world which he did not make and which he could not possibly have made because he was the thought of a Thought, nor did he know the self-awareness of ‘Him who is.'”

So Aristotle was not without error, but Aquinas did not accept this understanding “uncritically.” Aquinas revolutionized metaphysics by emphasizing existence. In his introduction to Aquinas’ “On Being and Essence” Armand Maurer writes, “This was a decisive moment in the history of western metaphysics, for St. Thomas was transforming previous Greek and medieval conceptions of being, which gave primary place to form.”

This hardly sounds like someone who accepted Aristotle’s philosophy uncritically.

But what about natural theology? Does Aquinas put a limit on natural theology?

First we must define what natural theology is. We do not find a definition in Anderson’s blog; however, we shall go to the man in question to see how he defines natural theology.

For Aquinas, natural theology is a way “to demonstrate the preambles of faith, which we must necessarily know in [the act of] faith. Such are the truths about God that are proved by natural reason, for example, that God exists, that he is one, and other truths of this sort about God or creatures proved in philosophy and presupposed by faith,” as he states in commentary on De Trinitate of Boethius.

Aquinas’ system begins in reality and uses reason to demonstrate God’s existence by reasoning from effect to cause.

His Five Ways are logical arguments that seek to demonstrate the existence of God by use of first principles (e.g. the principle of existential causality, the principle of finality, etc.)

Brian Davies points out in “The Thought of Thomas Aquinas” that Aquinas’ Five Ways are not intended to be the end all be all of arguments but are only a way to get the ball rolling, so to speak. These arguments do not intend to show that God exists with all the traditional attributes. The Five Ways are a posteriori demonstrations of God’s existence via change, efficient causality, contingency, degrees of perfection, and telos or finality.

When read in context, one can see that Aquinas uses the Five Ways as a starting point and then develops from there what must be true of God.

Anderson says that his own “approach has been to use arguments to prove parts of this definition rather than expecting any one argument to conclude, ‘and this all men call God,’” he continues, “that overextension is where the problem lies.”

As a response to this charge, I think the non-Thomist, analytic philosopher William Lane Craig says it best in his book “The Cosmological Argument from Plato to Leibniz,” in it Craig says, “Thomas’s proofs for the existence of God encompass the whole of Ia. 2-11 in the Summa Theologiae. Modern readers, used as they are to anthologized versions of Aquinas’s Five Ways, all too often fail to grasp this important point. Aquinas is sometimes criticized for what is thought to be his overhasty conclusion, ‘…and this is what everybody understands by God’; but this misunderstanding only arises by tearing Aquinas’s proofs out of their proper context. It is not until the finish of question 11 that the existence of what we mean by ‘God’ has been demonstrated.”

The Five Ways then use reason to demonstrate that God exists, then builds upon them to show who God is by reasoning what must be true of God. By this estimation, Aquinas has not limited natural theology but provides a great example of how to use the classical method of apologetics.


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