Aquinas’ first cause argument is the second of his three versions of the Cosmological Argument, which form the first of his three ways to God in the first part of the Summa Theologica.  As a Cosmological Argument, Aquinas’ first cause argument starts from the observation of order, in this case causation, in the universe.  The word “Cosmological” derives from the Greek “Kosmos” which means both “order” and “universe”.  As Anthony Kenny[CV1]  explains, Aquinas relies on Aristotle’s theory of causation, as outlined in the Metaphysics Book IV.  Aristotle argued that all things in the universe have four causes, which can by understood in terms of the material, efficient, formal and final.  Material causes are the physical ingredients of things, efficient causes the agents that cause them to exist as they do, formal causes the definitions of things which make them what they are and the final cause to which things aim is their goal or telos and ultimately flourishing.  Focusing on efficient causation, Aquinas’ second way to God argues that everything in the universe is caused by one or more agents outside itself and nothing causes itself to exist.  If this is so then there is a problem – what was the first efficient cause.  An infinite chain of efficient causes makes no sense, because without a first cause nothing would exist.  Something cannot come out of nothing.  There must be a first efficient cause, but this must itself be uncaused, which makes it unlike any other thing.  The uncaused cause of the universe could then be said to be “neither something nor nothing” and, Aquinas concludes, this is what everybody calls God. As an inductive argument the conclusion of the Cosmological Argument, that God exists, is supported by observed premises which are falsifiable.  Because of this, Aquinas’ first cause argument cannot be said to prove God’s existence.  The problem of induction ensures that the most that the argument can be said to achieve is a very high degree of probability that its conclusions are, in fact, true[CV2] . Leaving the problem of induction and the issue of proof to one side: Aquinas’ first cause argument is still a convincing argument for the existence of God and, as William Lane Craig continues to argue, it is a useful means of defending the rationality of faith[CV3] . 

An immediate criticism of Aquinas’ argument is that it assumes that EVERYTHING in the universe is caused.  Although this claim is supported by Aristotle, it may be fair to suggest – as indeed JL Mackie did in “The Miracle of Theism” (1982[CV4] ) – that there may be things in the universe that are uncaused.  Indeed, Quantum Physics has concluded that there are sub-atomic particles that are in a sense uncaused. It could be that Aquinas’ first premise – that everything in the universe is caused – is untrue and if that is the case then the argument would fail. Nevertheless, it would be going too far to suggest that Physics has proven the existence of uncaused things in the universe.  Quantum particles could well be caused, for all we know, even though they appear not to be.  The most that Mackie’s criticism achieves is to show that Aquinas’ first premise must remain uncertain.  Although it seems likely on the basis of present experience that all things are caused, as Hume observed it is always possible that there are things in the universe that are uncaused and that these could explain the universe without recourse to God[CV5] . In this way, although Aquinas’ first cause argument is not entirely successful as an argument for God’s existence from observation, it is able to survive an obvious line of criticism.

In Dialogues Concerning Natural Religion (1779) Hume went on to suggest that the universe itself could be the uncaused cause of itself.  Russell made a similar point in his debate with Frederick Copleston[CV6] , suggesting that the universe should be seen as a “brute fact”.  This is certainly possible; Aquinas’ might be guilty of committing the fallacy of composition in reasoning that just because things within the universe need causes that the universe as a whole needs a cause.  Russell gave the analogy of mothers – just because all men have mothers doesn’t mean that the human race has a mother.  While Hume and Russell could well be right and the universe might be the cause of itself, this goes well beyond our experience.  It is just as difficult to theorise about the universe being self-causing as it is to theorise that it has an uncaused cause.  Neither conclusion can be drawn with any degree of confidence.  What does seem certain is that Aquinas is correct to reason that the universe must be explained in terms of something that is uncaused, whether that is within the universe, the universe itself – or God.  William Lane Craig[CV7] , in adapting the Cosmological Argument for modern Christian Apologetics, chooses to leave the argument at its first conclusion – that there must exist an uncaused causer.  He leaves it to Theologians to convince people that the uncaused cause is in fact “what everybody calls God” and it seems that his caution is sensible. Neither Aquinas’ first cause argument nor any other version of the Cosmological Argument can conclusively prove the existence of God, but the argument can point to the rationality of faith given the necessity for a cause for the universe which is unlike anything within our normal experience[CV8] .

Immanuel Kant advised such caution when in the Critique of Pure Reason he argued that the Cosmological Argument, like other inductive arguments for God’s existence, goes beyond the boundaries of what we can claim to know.  It is reasonable to observe that all things are caused and that there is a tension implicit in this which demands explanation – but it is not reasonable to draw conclusions about that explanation when they go beyond possible experience.  Perhaps this is where faith comes in; the first cause argument cannot successfully PROVE the existence of God, but it can point towards a mystery which is evident in the observed universe, a mystery which is suggestive of the existence of something supernatural if not of the God of Classical Theism.  As Hume pointed out, the first cause argument cannot claim to lead to the God of Christianity – even to a single God in fact – but limited as it is, the argument provides a useful defence for the believer[CV9] . 

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 [CV1]Precise relevant detail and range of scholarly views

 [CV2]Acknowledging & engaging with the precise wording of the title – This also works to show the LIMITATIONS of the argument.

 [CV3]THESIS

 [CV4]Using a range of scholarly views.  This paragraph also serves as the COUNTERCLAIM, as it does cede some of the point that Mackie makes.

 [CV5]Evaluating the “maybe not everything has a cause” criticism, linking to the THESIS, justified, developed…

 [CV6]Range of scholarly views – again a bit of counterargument (balance) here, allowing that Hume and Russell have a point.

 [CV7]Range of scholarly views

 [CV8]Evaluating the fallacy of composition criticism and linking to the THESIS – justified, developed, sustained…

 [CV9]Drawing in Kant’s criticism & another of Hume’s in drawing the final CONCLUSION, which restates the THESIS – successful argument.  Builds step by step and is therefore convincing.