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The Validity of Aquinas’ Third Way

· 6 min read

(This is my research essay for Year 12 Philosophy)1

Thomas Aquinas’ Third Way is a deductive argument for the existence of God. The argument from contingency and necessity derives from the concept that there is a necessary being capable of bringing contingent things into existence. Aquinas’ reasoning is indeed cogent because its premises provide a plausible argument for God’s existence through the existence of the universe. In this paper, Aquinas’ Third Way will be evaluated and shown to be a convincing argument. Bertrand Russell’s objection will be assessed and shown to be an implausible argument.

As an a posteriori argument, Aquinas begins the Third Way with a fact understood through experience, that something contingent exists (Reichenbach 2017). By contingent, Aquinas is referring to beings that depend on something other than themselves for their existence. For instance, human beings are contingent because we depend on water and food. This is true since we cannot survive without something other than ourselves. We would technically cease to exist if we stopped depending on it. Therefore, in a sense, all contingent beings do not have to exist. Aquinas takes this concept further and augments it in his first premise, stating that “everything that exists in the natural world is contingent.” He emphasises that the things which make up the universe require an explanation for why they exist because they did not have in the first place. The premise is valid for the reason that the natural world is purely the sum of all the contingent beings (Creel 2013). Therefore, the natural world is also contingent, and we need a justification for its existence. Since the parts which make up the natural world did not have to exist, the world does not have to exist as well. Hence, we would also need an explanation for the universe’s existence.

The second premise of The Third Way states that “contingent things require something else to bring them into existence.” Here, Aquinas emphasises that the natural world only exists because something else brought it into existence (Reichenbach 2017). This premise is accurate because it cannot be the case that contingent things come into existence out of nothing. As a famous Latin statement puts it, “Ex nihilo nihil fit” (“Nothing comes from nothing”). Because nothing has no potentiality, where absolutely nothing is present, nothing can come into existence (Creel 2013). On the other hand, anything that has potentiality is considered as something rather than nothing. Hence, to explain the existence of the natural world, we must go beyond contingent beings to say that it was brought into existence by a greater being. Furthermore, Slavko Gujić (2003) states that “nothing is nothing, because it needs nothing to be nothing.” This statement is also true because nothing derives from itself. Since nothing is essentially the absence of all properties, it is impossible for something contingent to be nothing as there is something present. Following the first premise, Aquinas proclaims that the natural world requires something to bring it into existence. This implies the idea of a being that is not contingent had existed before the universe.

Bertrand Russell refutes the Third Way because it allegedly commits the fallacy of composition. That is, just because some things are contingent, it does not mean that the whole universe is contingent as well. According to Hodder Education (n.d.), the ‘fallacy of composition’ implies that something is true of the whole from the fact that it is true of part of the whole, or of every part of the whole. An example of this fallacy includes suggesting that a brick wall is small because the bricks in the wall are independently small. This is a fallacious argument because it assumes that what is valid for the bricks is also true for the wall as a whole. For Russell, the Third Way commits this fallacy because we can say that the natural world itself is necessary. As he stated in a radio debate, “the universe is just there, and that’s all” (Hick 1964). He is ultimately assuming that the universe exists as an unexplainable brute fact (Hodder Education n.d.). While there are some sensible points raised by Russell, his objection is invalid because it does not examine the content of Aquinas’ argument. Occasionally, the concept that is true for a part of a whole can also be true for the whole (Reichenbach 2017). For example, the wall is brick (made of clay) because it is built of bricks (made of clay). The contingency of the natural world resembles this. If the contingent things that make up the universe cease to exist, then the universe itself, which is no more or less than the total of its parts, can also cease to exist (Reichenbach 2017). Therefore, if the universe ceases to exist, it is contingent. Hence, Russell’s objection is implausible.

Aquinas concludes his argument with a strong inference and a valid conclusion. The inference between the second premise and conclusion implies that the natural world was brought into existence by a greater being. This is quite robust because necessary beings are the only ones that are capable of bringing contingent things into existence. As previously mentioned, contingent things, such as the natural world, require something else to make them exist. The only being which is capable of doing this is one that is not caused and does not depend on anything else for its existence. That is, a being that exists is necessary. Aquinas concludes his argument by asserting that “there has to be a necessary being which is capable of bringing things into existence.” He states that the most plausible candidate for this necessary being is God himself (Creel 2013). Hence, it can be said that the existence of contingent beings is evidence for the existence of God. Aquinas’ conclusion is valid because God is the only being capable of making the natural world exist. As Anselm once said, God is a “being than which no greater can be conceived” (Fordham University 2020). This is also true as God is both transcendent and immanent. Given that both premises of the Third Way are logical, it is evident that the conclusion brought upon is true as well. This ultimately makes the whole argument cogent.

Aquinas’ Third Way is an intriguing argument for the existence of God. It accurately emphasises how everything in the natural world is contingent, which is true as most things depend on something else for survival. The argument then states that these contingent things need something else to bring it into existence. Moreover, since the universe itself is also contingent, it requires a necessary being capable of bringing it into existence. This necessary being understood to be God. While Russell’s objection assumes that the argument is a fallacy of composition, it ultimately does not because his objection does not examine the context of Aquinas’ reasoning.

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Footnotes

  1. I am impressed by how my 17-year-old self wrote this. Thank you to my Great Uncle Fra Tvrtko Gujić for inspiring me. ↩