An Analysis of Aquinas’s Cosmological Arguments

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An Analysis of the Ontological Argument for the Existence of God Logical Theist

In this episode, I analyze one of the most interesting arguments for the existence of God, the ontological argument. Read the corresponding blog post here. Podcast theme music by Learn how to start a podcast here.

Thomas Aquinas was a medieval Christian philosopher who is known as one of the most important figures in the history of the Catholic Church. One of the things that he is most known for is his five arguments for the existence of God, which are found in Aquinas’s Summa Theologica (Summary of Theology). Four of these are cosmological; that is, they argue for God as the origin or cause of various aspects of the universe or of the universe as a whole. (But it should be noted that these are not the same as creationist or intelligent design arguments.) Thomas Aquinas also presented a teleological argument, which argued from perceived intelligent design. This one is more similar to recent creationist arguments, although it is still not exactly the same and seems general enough that it could allow for acceptance of biological evolution. With all of that said, I will only be analyzing the four cosmological arguments for the existence of God, proposed by Thomas Aquinas.


The first argument which Aquinas presents is from motion. This and his other four arguments for the existence of God are explained in the Third Article of the Second Question in the First Part of his Summa Theologica. I will quote a portion of it here:

It is certain, and evident to our senses, that in the world some things are in motion. Now whatever is in motion is put in motion by another, for nothing can be in motion except it is in potentiality to that towards which it is in motion; whereas a thing moves inasmuch as it is in act. For motion is nothing else than the reduction from potentiality to actuality. But nothing can be reduced from potentiality to actuality, except by something in a state of actuality. . . . Therefore, whatever is in motion must be put in motion by another. If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; . . . Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.

First, it should be noted that Thomas Aquinas’s concept of motion as presented here is clearly not the same as Isaac Newton’s laws of motion. Rather, Aquinas’s definition is more philosophical and broader than the Newtonian laws. However, it is inappropriate to compare the two definitions of motion, especially since modern natural science had not yet been introduced. It is more appropriate to see whether the definitions relate to each other in the same sense and whether they contradict each other if they are meant in the same sense. Aquinas’s concept of motion is merely potentiality to actuality. This can be applied to something going from being potentially dead to actually dead. The example that Aquinas gives is wood going from being potentially hot to being made actually hot by fire. On the other hand, Newton’s laws deal more with motion as we normally think of it in modern times, that is, in terms of movement. Thus, Aquinas’s idea of motion and Newton’s are not meant in the same sense.

Now, an important point made in this argument is that the sequence of reduction from potentiality to actuality cannot be infinite. Because Aquinas believes that this sequence cannot be infinite, he also believes that the we must eventually arrive at a “first mover,” that was itself (or himself) not moved, that is, a mover that has always existed in a state of actuality. This “fist mover” he says is God.

Assuming that it is indeed illogical for the sequence of reduction to be infinite, then the rest of the argument appears to be valid up to the final claim that the first mover must be God, although he only says that “this everyone understands to be God.” However, this is admittedly a leap in logic, since nothing in the argument itself necessitates that the first mover be a being. And really, the question of whether the first mover must be God is really a question of whether the first mover is a being. After all, if it is a being, then it makes perfect sense to refer to this being as God.


Let’s move on now to Aquinas’s second cosmological argument. I will quote it below:

In the world of sense we find there is an order of efficient causes. There is no case known (neither is it, indeed, possible) in which a thing is found to be the efficient cause of itself; for so it would be prior to itself, which is impossible. Now in efficient causes it is not possible to go on to infinity, because in all efficient causes following in order, the first is the cause of the intermediate cause, and the intermediate is the cause of the ultimate cause, whether the intermediate cause be several, or only one. Now to take away the cause it to take away the effect. Therefore, if there be no first cause among efficient causes, there will be no ultimate effect, nor any intermediate cause. But if in efficient causes it is possible to go on to infinity, there will be no first efficient cause, neither will there be an ultimate effect, nor any intermediate efficient causes; all of which is plainly false. Therefore, it is necessary to admit a first efficient cause, to which everyone gives the name of God.

In this argument, Aquinas basically makes an argument from causation. And similar to his previous argument, he argues that efficient causes cannot go on to infinity. If efficient causes cannot go on to infinity, then obviously there must have been a first efficient cause, which he argues must be the case because there cannot be an ultimate effect without intermediate causes, which in turn cannot be if there be no first efficient cause. Then he states that it “is plainly false” that there is no ultimate cause and no intermediate causes. Perhaps, he calls this “plainly false” if by ultimate effect he means those things which exist today. In other words, because things exist, there must have been intermediary causes and, thus, a first efficient cause.

Again, one will notice, that nothing within the argument itself necessitates that the first efficient cause must be God, unless one defines God as synonymous with the first efficient cause, in which case God does not even need to be a being. However, God is generally defined as a being. Therefore, if this argument reduces God to merely being the first efficient cause without necessitating that the first efficient cause be a being, then the argument simply changes the general definition of God; thus, the point of the argument, to demonstrate the existence of God, seems to remain undemonstrated.


As for his third argument, I will present a portion of it below:

We find in nature things that are possible to be and not to be, since they are found to be generated, and to corrupt, and consequently, they are possible to be and not to be. But it is impossible for these always to exist, for that which is possible not to be at some point is not. Therefore, if everything is possible not to be, then at one time there could have been nothing in existence. Now, if this were true, even now there would be nothing in existence, because that which does not exist only begins to exist by something already existing. . . . Therefore, not all beings are merely possible, but there must exist something the existence of which is necessary. But every necessary thing either has its necessity caused by another, or not.

By now, you can probably see where Thomas Aquinas is going with this. He continues to explain his argument, making the point that he considers it to be impossible that there be an infinite regression of necessary things. Therefore, there must have been a first necessary thing, whose necessity was uncaused. Again, Aquinas makes this synonymous with God.


Finally, we come to the fourth argument. Quoting Thomas Aquinas:

Among beings there are some more and some less good, true, noble and the like. But more and less are predicated of different things, according as they resemble in their different ways something which is the maximum, as a thing is said to be hotter according as it more nearly resembles that which is hottest; so that there is something which is truest, something best, something noblest, and consequently, something which is uttermost being; . . . Therefore there must also be something which is to all beings the cause of their being, goodness, and every other perfection; and this we call God.

In this argument, Aquinas is basically arguing that there must be a standard according to which we compare different qualities, including being and goodness. The ultimate standard, he says, is God. Although this one does attempt to make an argument for God that actually argues for a prime being. However, an objection which immediately comes to my mind is this: how can being be considered a means of comparison? If by being, he means mere existence, then existence is hardly a comparative quality and is certainly not a quantity. Either something exists or does not. Furthermore, how two beings can be compared in terms of an ontological hierarchy is not nearly as clear as measuring goodness. Things that do exist on a higher level than another are not so because they have more existence than that which is below it, as if existence could be measured.


The fourth argument, to me, seems to ultimately fail. The first three, however, are over all strong arguments, but they unfortunately do not necessarily demonstrate the existence of God, unless the definition of God is redefined as what those arguments conclude must exist. It is also important to note that these arguments do make assumptions. For example, the first three arguments assumed that certain regressions cannot possibly be infinite. Also, they assume that God must necessarily be the origin of these regressions. However, it does seem more intuitive to assume that these regressions are finite rather than infinite if these regressions are linear and not circular. If they are circular, it does make sense to view them as infinite.

With all of that said, these arguments are still good starting points and at least make it reasonable to believe in the existence of God. And it should not be considered too big of a leap in logic to say that the first mover, first efficient cause, and the first necessary thing. After all, if one can come to accept those, then the next question is whether these must be an intelligent being. It is certainly neither impossible nor illogical that they (the first mover, the first efficient cause, and the first necessary thing) are an intelligent being, even if it is not necessitated that they be.

Furthermore, the idea of the universe being infinite or the idea that the sequence of all events in the universe is circular rather than linear are both speculative rather than definite. As far as we have observed of the known universe, everything appears to be finite. In addition, according to the law of conservation of mass and energy, mass and energy can be neither created nor destroyed. And according to the second law of thermodynamics, the amount of entropy (that is, disorder) increases in a closed system until it reaches a maximum. Thus, if the universe is a closed system, the lifespan of the universe cannot be infinite or eternal. If we live in a multiverse, then the multiverse can be defined as the sum of its parts, as with anything else that has parts. If each universe within the multiverse is finite, the multiverse must also be finite, seeing that the multiverse can be defined as the sum of its parts. However, if the multiverse is infinite and if each universe is an open system, it is possible that our universe is infinite. Still, another question would be whether the multiverse is infinite insofar that it is ever-expanding. If the multiverse is ever-expanding, it is continuously moving from potentiality to actuality. Therefore, there must be something prior to the multiverse that would have set it in motion. Of course, this is a lot of speculation, and I can go on theorizing. But for now, I believe that I have said enough for one blog post. 

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