Like any good Christian, Aquinas believed in god. His proof of God is simply known as “The Five Ways”. Each way, of course, is a different way of understanding proof of God’s reality. Coming from an Aristotelian perspective, he engaged with God in a unique methodology.
Aquinas starts off his proof in a true medieval way, by setting up opposing positions as a dialog. In this case, it is the idea that God either cannot be proved because he is self-evident or because he must be taken on faith. Each position is set against each other as though each belonged to an interlocutor. This is the “questio” or “question”.
In this form of argumentation, a question would be proposed which could be given either a “yes” or a “no” answer. From here, one would assemble all the best arguments for one’s side of the debate; in Aquinas’s situation, he would start by finding all the best arguments for “no” and he would be able to use any material from an important person in the field. After this, one would set forth one’s one views and give the argument for said views. This is the point where one would argue and deconstruct the minute fallacies and ideas present within the opposing camp.
Such a method was known as the “Scholastic Method” since it grew out of the schools. People who adhered to this method were known as “scholastics” whereas those who opposed it used the term as an abusive slur believing the reliance on citation to stifle genuine thought. At its core, though, Scholasticism’s aim was to rectify the mistakes of the past via minute argumentation and experimentation. Only through such attention to detail could progress be made.
Following this method, Aquinas then lays out the argumentations: he lays out his view—the existence of God can be proved; then, he identifies two objections to that view: “It is impossible to prove the existence of God because the existence of God is self-evident” (re this is how Aquinas understands Anselm). To Aquinas, there are two kinds of self-evidence: what is evident in an absolute sense and what is self-evident to us; one can comprehend that every Bachelor is single since we understand the concepts involved but we cannot understand the concept of God until the next life, ergo, the distinction is vivid.
The second objection to Aquinas’s claim is that God’s existence must be taken purely on faith. This argument takes off directly from the first argument in that because we cannot have any direct insight into God’s nature there is no way to prove that he exists; if we have no insight into his nature then how could we prove that he exists? It would be like trying to prove the existence of Strong Theory without even understanding rudimentary physics. Aquinas, then, uses the “quia” argument where one reason backward from the effects to the cause. This argument is especially useful to Aquinas since it doesn’t require any insight into God himself, merely something here on Earth which is indicative of God’s activity. This is the sensible things placed on Earth by God.
But, this raises a new question. Because God has nothing in common with sensible things how could these things help us learn anything about God? Aquinas responds by simply saying that because sensible things are the reminder of God they can give us some hints about his activity—not himself but his activity. Understanding sensible things will only result in us knowing a tiny bit about God (hence, why there is “mysteries of the faith”). Aquinas then admits that we cannot have any insight into God’s nature while still retaining some knowledge about God from rational reasoning.
From here, Aquinas lays out his five ways. Professor Williams just briefly lays out each of the five ways.
Way one deals with motion. We look at the sensible world and see motion. We then reason that there must be a non-moved entity which set the motion into motion. The second way is that some things cause other things. We look at the sensible world and see relations of cause and effect. From this, we then reason that there must have been an originating cause and not an effect. The third way argues that some things are contingent. These are things capable of both existing and not existing. Aquinas argues that in order to understand these contingent beings there must be a non-contingent being, a being which is not capable of not existing. The fourth way concerns the idea that some things are more perfect than others. On this basis, it reasons that there must be a “maximumly” perfect being, one so perfect that exceeds all other possible perfection. The final way, meanwhile, is that some things engage in an apparently purposive behavior. Here is the belief that sensible things strive toward some kind of end which their behavior strides toward. On this basis, there must then be an intelligent being which directs them to obtain those ends or goals.
Professor Williams looks in detail at Aquinas’s “first way”, that which was called the “clearest way” by Aquinas himself.
This way is a good way since it allows people to see how to argue for the basis of God while still retaining Aristotelian principals. Aquinas begins by saying that it is clear to our senses that some things are in motion. This is a complicated claim since the Latin for “motion” (“motos”) has a wider meaning than in contemporary English. Aquinas, following Aristotle, distinguished three kinds of motos: change of quality, change of quantity, and change of place. Aristotle also distinguished “actuality” and “potentiality”, that is, “I am actually thin” but “potentially fat”; such a conception was then given to the three ideas of motion (see above). Though, Aristotle and Aquinas give that a thing can’t be both in “actuality” and “potentiality” in the same place at the same time. This is deep since it means something must cause something to go from potentiality to actuality. Whatever causes this transition, it will be in actuality (something that is potentially some way, after all, cannot cause a definite reaction if it is not that way; a white fence requires blue paint which is actually blue instead of paint which is potentially blue). In this case, the mover must be distinct from the things which are to be moved: the moved thing must be in potentiality while the mover in actuality; neither can be both actuality and potentiality at the same time (water cannot be actually hot and potentially hot; if it is actually hot, then it is actually hot, not merely potentially hot). This is the first main premise of the first way.
Because we know that all things are in motion and these things require a mover, we must ask ourselves: Does this process go on indefinitely or does it come to a halt at some point? Is there an infinite chain of movers or would we discover a mover who is unmoved? Aquinas then argues that there cannot be an infinite chain of regression. The chain does come to an end and we must come to an unmoved mover.
To understand this, consider a twelve-car pileup where one car slams on its breaks and successive cars slam into that car. If the first car had never slammed on its breaks, then there would not have been any pile up; if you take away the first mover then there is no movement. As Aquinas points out, in an infinite series, there is no first mover. If there is no first mover then there would not be motion but clearly, there is motion. Therefore, the series of movers and things moved is not infinite. This first mover is God.
Still, this argument does lack finesse. After all, we only know that the unmoved mover sets motion into motion, we do not know explicitly whether he is a god; in the very least, we still don’t know any attributes of this mover, whether he is perfectly good or perfectly knowledgeable and so forth. Even so, we can still get far in understanding how the universe got started.

3 thoughts on “Aquinas’s Proof of an Unmoved Mover (Notes:72)

  1. Hi! You state that Aquinas’ argument lacks “finesse.” However, the Five Ways are merely summations, not full-scale arguments. He elsewhere fully explicates every step of his argument in De Ente et Essentia.

    Now, one may of course disagree with his arguments, but it is incorrect to assume that he did not rigorously attempt to demonstrate the existence of God, including His aseity and goodness.


    1. Hi Scalia,

      Thank you for linking us to De Ente et Essentia, I am sure future readers will appreciate the further reading.

      I will accept your criticism and agree that summations are not meant to be full-scale arguments. But, these notes are just my own scribblings following along to a Great Courses lecture (see the “Labels” at the end of the post), so they are not really my own opinions. All the same, thank you for the clarification.



  2. Thanks, Curtis, for the additional info. Aquinas is often attacked for jumping to the “God conclusion” by atheists who are unfamiliar with his writings. I apologize for lumping you in with them.


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