Thomas Aquinas is one of the most influential Western thinkers. He had a massive influence on Roman Catholic theology, but also on Western philosophy. He is one of two medieval philosophers that you will always find in textbooks of historical philosophy (the other is Augustine). Aquinas is famous for developing his “five ways”, which are five arguments that show the existence of God. One of these ways is Aquinas’s version of the cosmological argument. This argument is similar to the others, but it provides an interesting nuance on the points already made. The argument can be basically stated as follows:
Everything that exists is moved either by itself or by something other than itself.
The universe (and everything in it) are moved movers (caused causes) (they are moved by something other than themselves)
The chain of moved movers (caused causes) cannot be infinite.
Therefore, there must exist an unmoved mover (an uncaused cause).[i]
The most controversial premise will probably be premise two, that the universe represents a moved mover (a caused cause). This may be seen from the fact that the universe is contingent (it might have failed to exist). The fact that the universe might have failed to exist raises the question of why it exists in the first place. If it might have failed to exist, we would expect there to be some cause that has brought it into existence. We also know from current scientific cosmology that the universe began to exist (at the Big Bang) which means that it probably has a cause (and so would be a moved mover).
You might say that Aquinas’s argument relies on a primitive understanding of physics. Nevertheless, the principle of Aquinas’s argument remains just as valid then as it does today, even given our understanding of physics. Impersonal mechanisms cannot “start” themselves. They require something to start them. This can be more impersonal mechanisms, but at some point, the chain of causation needs to terminate in some metaphysically necessary being that can start these mechanisms and does not require to be “started” itself. It is absurd to think that a chain of causes is infinite in the past, because that would mean that we would never “arrive” at the cause of the universe or the cause of your existence. If the chain of causes is infinite in the past, then we would need to traverse an infinite chain of causes to get to the cause of the universe or the cause of your existence. (For more information about the absurdity of an actual infinite, see the Kalam Cosmological Argument). Thus, the chain of causes must terminate with something. This being must be uncaused, because otherwise it would not terminate the infinite regress. This argument form is called a reductio ad absurdum. It proves its conclusion by showing a contradiction in the alternative view. The alternative view (an infinite regress of causes) would imply that we should not exist (yet). But we do exist (that’s the contradiction). If there can’t be an infinite regress of causes, the chain of causes must terminate somewhere. The only way it could do that is if that something is uncaused.
Why is the explanation God?
If it is established that the universe does require a cause, why should that cause be God? Whatever is responsible for the universe, must transcend what the universe is made of, because whatever it is, it exists apart from the universe. Thus, it can’t be constituted by things or be dependent on things that only came into existence with the universe. That is, it must transcend matter, space and time. Thus, it must be immaterial, timeless and spaceless. It must also be a person. William Craig notes “the personhood of the cause of the universe is implied by its timelessness and immateriality. The only entities we know of which can possess such properties are either minds or abstract objects, like numbers. But abstract objects do not stand in causal relations…Numbers, for example, cannot cause anything.”[ii] Also, the universe cannot be accounted for by science, for at least two reasons. First, science always explains things naturalistically. However, the universe cannot be explained naturalistically since it represents the totality of natural reality. It would need to be explained with reference to itself, which would just be illogical. One needs to appeal to something other than the thing needing to be explained in order to explain it. Secondly, science explains phenomena by identifying regularities or laws that operate on conditions. However, since there is nothing outside of the universe (or multiverse, whichever you prefer), it cannot be explained through regularities and laws. Natural laws “organize” preexisting material. However, those laws cannot account for how the universe came into being, because there is nothing outside the universe for it to organize. The only other type of explanation we are familiar with is personal explanation: explanation with reference to the intentions and actions of persons. Thus, the universe must have a personal explanation.[iii] Thus, the universe must have been caused by a timeless, spaceless, immaterial person.
Who Designed the Designer?
The argument implies that the thing that causes the universe must be an uncaused case. In other words, the uncaused cause can by definition not have a designer.
Why ‘God’ and not ‘Gods’?
Why shouldn’t we think that many gods came together to design the universe? The simplest conclusion is that there is only one. If we are satisfied that the argument proves some sort of designer, there is no need to multiply entities beyond what is metaphysically required (i.e. Ockham’s Razor). The principle of ontological parsimony would counsel us that where the evidence is the same for either of the above propositions, we should opt for the simpler one: the one that postulates the fewest entities. I could similarly postulate that many gods came together and then they had a huge supernatural fight. The universe was spawned out of this celestial clash of powers. This theory explains the conclusions of cosmological and teleological arguments, but it is invalid as a conclusion precisely because we have no evidence for such a complex story (and it therefore contradicts ontological parsimony). It is therefore unreasonable to suggest that natural theologians have to rule out every logically possible scenario of creation. Similarly, scientists do not need to rule out every logically possible explanation of the evidence but can comfortably settle with the simplest one.
The world does not conform to our intellectual preferences
It is somewhat common for atheists to attempt to refute cosmological arguments by saying that our rational intuitions cannot be applied to the very macro or the very micro. Or, our rational intuitions cannot be applied to the conditions of the cosmos, because these intuitions developed in a world of medium-sized objects. For example, J.L. Mackie contends, “We have no right to assume that the universe will comply with our intellectual preferences.”[iv] It is astounding that he should say this however, since the scientific method and all our reasoning about the world, is ultimately based on intuitions like those that underlie the principle of sufficient reason (which he calls our “intellectual preferences”). Daniel Dennett and the popular atheist vlogger, Thunderfoot, make similar points when considering the arguments of William Craig.
Firstly, this objection assumes naturalistic understanding of human beings and is therefore circular. It assumes that only natural causes are responsible for our intellectual intuitions, which assumes naturalism in order to argue for it. Secondly, this objection has a fairly absurd implication. Scientific cosmologists probably use modus ponens, modus tollens and other basic syllogisms to make conclusions about the universe as a whole. But, if our intuitions about modus ponens and modus tollens are empirically constituted and only developed through natural causes, then scientists are also doing what these atheists have said we cannot do. The intuitions of those scientists are not special – they also developed in a world of medium-sized objects. So why can scientists use those same intuitions in scientific cosmology? Scientists may have some advanced theorems at their disposal, but all this is based on intuitions very much like the one underlying the principle of sufficient reason. In other words, no matter how advanced a mathematical theorem theoretical physicists may deal with, they are guided at every step of implication by these basic intuitions. Scientists regularly make use of the more basic forms of reasoning in forming their conclusions. Those complex mathematical models are all based on rational intuitions, which are supposedly useless when dealing with the very small or the very large. The problem with contending that our intellectual intuitions are suddenly invalidated when we deal with the “very large” or “very small” is that scientific endeavor in these areas are also then become problematic.
[i] Thomas Aquinas, “The Classical Cosmological Argument”, in Philosophy of Religion: Selected Readings ed. Michael Peterson, William Hasker, Bruce Reichenbach and David Basinger, 4th ed. (New York: Oxford University Press, 2010) 184 – 186
[ii] William Lane Craig, Reasonable Faith, (Wheaton: Crossway, 2008) 153
[iii] Ibid., 152
[iv] J.L. Mackie, The Miracle of Theism, p. 87