Aquinas’ Cosmological Argument fails to demonstrate the existence of the Christian God.  While the first, second and third ways offer some support to the belief that there must be a Prime Mover, Uncaused Cause and Necessary Being, In the Summa Theologica 1,2,3 Aquinas only asserts that “this is what all men speak of as God.”  Indeed, taking the Prime Mover as an example, it could share only some of the characteristics of God as He is normally understood.  While the Prime Mover is certainly transcendent and immutable, the extent to which it could be omnipotent or omniscient, let alone omnibenevolent or immanent, is slight and unconvincing.  Nevertheless, putting this criticism aside, Aquinas’ Cosmological Argument successfully demonstrates the existence of a transcendent explanation for the Kosmos.

Firstly, in Dialogues Concerning Natural Religion Hume’s character Philo criticised the Cosmological Argument, asking how anybody can be certain that everything has a cause. While it is true that the observed laws of nature which form the premises of Aquinas’ argument depend on observations which are necessarily limited within time and space, questioning whether such observations can be taken to be fair and representative attacks the Cosmological Principle on which all science depends.  Newton was the first to express the Cosmological Principle, the assumption that “viewed on a sufficiently large scale, the properties of the universe are the same for all observers” or in other words that the universe is homogenous and isotropic and more fundamentally, that the way we observe the universe is the way it really is and that this is a fair and representative sample of the whole. In asking whether there might not be uncaused things in the universe despite the fact that these have never been observed, Hume’s criticism of the Cosmological Argument constitutes a sceptical attack on the human ability to use observations as a basis for understanding the Natural Laws which govern the universe, so by accepting this criticism we lose far more than one approach to demonstrating the existence of God.  It follows that Aquinas’ argument survives Hume’s first criticism and demonstrates the existence of a transcendent “creator”. 

Secondly, Hume’s character Philo goes on to ask why the cause of the universe, if such there is, would have to be intelligible.  This criticism is no more effective than the first.  The whole point of Aquinas argument is to show that whatever caused the universe must be transcendent and beyond human understanding, impervious to the laws of motion, causation and contingency that govern everything else.  For Aquinas, the cause of the universe is “neither something nor nothing,” a necessary being that does not exist as things exist, contingently, but rather eternally and immutably outside the framework of spatio-temporal reality.  While Kant argued that necessary existence is so far beyond our experience to be beyond possible knowledge, Aquinas does not claim to be able to know or understand God, only to deduce that He exists, albeit mysteriously.  It follows that Aquinas’ Cosmological Argument survives Hume’s second criticism and Kant’s criticism as well, demonstrating the existence of a transcendent “creator”. 

Thirdly, Hume’s character Philo argues that Aquinas’ argument relies on the Fallacy of Composition, and indeed Aquinas does move from observations of movement, causation and contingency in the universe to claiming that the universe as a whole must be moved, caused and have something to depend on.  Russell used the powerful example of all men having mothers but the human race not having a mother to explain Hume’s point.  However, while it is fallacious to assume that characteristics of the part MUST be true of the whole, it is not impossible that they are true of the whole.  Aquinas (and more recently Craig) appeal to common sense as well as fallacious reasoning when they argue that given that everything in the universe is caused, the universe must also have a cause.  The alternative, that the universe is uncaused or, as Russell put it, a “brute fact” seems unacceptable to most people today, not least because the Aristotelian infinite-universe paradigm has been replaced by Big Bang Theory which shows that the universe had an absolute beginning.  Masses of Scientific evidence now supports the claim that the universe had a cause, even if that cause outside of the normal laws of nature and so transcendent, even if this was not a “creator” as this would normally be understood.  It follows that Aquinas’ Cosmological Argument survives Hume’s third criticism and Russell’s criticisms as well, demonstrating that the universe has a transcendent cause, if not a “creator” precisely. 

On the other hand, Aquinas’ Cosmological Argument falls short of providing rational support for faith in the transcendent creator-God of Christianity.  As Hume rightly pointed out, there is no way to show that there could not be multiple uncaused causes of the universe, let alone that the cause would be omnipotent, omniscient, omnibenevolent or in any sense personal or capable of becoming incarnate in Jesus Christ.  Nevertheless, the question did not ask whether Aquinas’ argument successfully reached the conclusion that God exists, but rather asked whether the argument successfully reached the conclusion that there is a transcendent creator.  A transcendent creator may, but also may not be, the same as the God of Christianity.  In this case, Aquinas’ argument demonstrates the existence of a transcendent entity that is responsible for initiating and sustaining the universe but no more. 

In conclusion, Aquinas’ Cosmological Argument successfully reaches the conclusion that there is a transcendent “creator” but does not demonstrate the existence of God. As William Lane Craig has argued, it is for theologians to determine whether the attributes of the transcendent cause of the universe can be reconciled with those of the object of religious faith.  This is why his Kalam argument stops with the conclusion “the universe must have a cause” rather than making the leap to saying “and this is what all men speak of as God” as Aquinas boldly does.