On Aquinas’ Five Ways
In his seminal work, Summa Theologica, the celebrated Christian philosopher, Thomas Aquinas, engages with the question of the existence of God. He notes that there are certainly objections to the claim that there exists such a divinity, but Aquinas believes that these objections can be overcome and that this existence can be shown to be well-founded. The eminent philosopher then lays out a list of arguments which he supposes to make this case. These arguments have come to be known as Aquinas’ Five Ways, and they have been so influential in philosophy that many theologians and apologists still cite them as if they are authoritative logical proofs, more than 700 years after the Italian priest set them to page. On the contrary, however, it seems that there are a number of issues which prevent Aquinas’ Five Ways from being quite so powerful, now, as they may have been in his own day.
The First Way is Aquinas’ Argument from Motion. The philosopher, being heavily entrenched in Aristotelian philosophy, means something different by “motion” than is commonly understood, today. When Aquinas says that a thing is “in motion,” he means that some change which has yet to occur is being made in that thing. In addition to spatial mobilization, this can refer to any sort of change—for example, a chameleon which is perfectly still, but changing colors, would be “in motion,” on Aquinas’ view. We can summarize this argument as follows:
- There are some things which are in motion.
- If a thing is in motion, that motion must originate in the action of some other thing.
- This chain cannot go to infinity, because there must be a First Mover.
- Therefore, there is a First Mover whose motion does not originate in the action of some other thing. (3)
Laid out in this fashion, it seems perfectly clear that Aquinas’ First Way is not even a valid argument, let alone a sound one. His third premise is a blatant instance of question begging. Aquinas asserts that there must be a First Mover, therefore there is a First Mover. Furthermore, the conclusion which he draws violates his second premise, making it a fairly clear example of special pleading. If Aquinas’ conclusion is true, then his second premise is false, invalidating the argument.
Aquinas’ dedication to Aristotle is again evident in his Second Way, the Argument from the Formality of Efficient Causation. Aristotle’s view of the notion of causation divided the concept into four categories: material, efficient, formal, and final. The “material” cause is that which is being changed, the “efficient” cause is the agent effecting the change, the “formal” cause is the manner in which the change occurs, and the “final” cause is the end purpose which drove the change (Aristotle’s Physics 2.3). Using an argument which is similar to his First Way, Aquinas argues:
- Changes have Efficient Causes.
- No change can be its own Efficient Cause.
- There cannot be an infinite chain of Efficient Causes.
- Therefore, there must be a First Efficient Cause. (1, 2, 3)
This argument is slightly better than Aquinas’ First Way, as this one is at least valid and free of overt logical fallacies. However, it is not necessarily sound. The third premise is fairly suspect, and Aquinas does not give very good support for it. The priest notes that in any series of efficient causes, a subsequent efficient cause is always the result of a prior. He then baldly asserts that there must be a first Efficient Cause. This, again, shows Aristotle’s influence on Aquinas, as the Greek philosopher was vehemently opposed to the notion of actually infinite sets of entities (Physics 6.1). Unfortunately for Aquinas, Aristotle’s understanding of infinity is nearly as antiquated as was his belief that the Sun, planets, and stars revolve around the Earth. Mathematicians and physicists have been regularly utilizing completed infinite sets in real-world applications for more than 400 years, now, and it has been nearly 100 years since the concept has even been a source of much controversy in the philosophy of mathematics. If Aquinas wants to demonstrate that there cannot be an infinitely receding chain of Efficient Causes, he must do a better job than to simply note the fact that this would imply that the chain lacks a first cause.
The Third Way is an Argument from Contingency. Aquinas points out that there are things which exist that exhibit the potential to not exist. Four centuries later, in a similar argument, Leibniz would say that such things are “contingent,” as opposed to “necessary” things—that is, things which cannot logically be non-existent. Aquinas’ Third Way is summed up as follows:
- Some things exist which have the potential to cease existing.
- If a thing can cease to exist, then there must have been a prior time in which it did not exist.
- If everything has the potential to cease existing, then there must have been a time when nothing existed. (1, 2)
- If nothing existed, nothing can have been brought into existence.
- Therefore, it cannot be that everything has the potential to cease existing, since (4) contradicts with (1).
There are two problems with this Third Way which are of particular concern. Firstly, Aquinas offers absolutely no justification for his second premise. It does not follow that a thing potentially ceasing to exist implies that it must have not existed at some time in the past. However, even if that premise is true, the most which Aquinas might draw from this argument is that there must exist at least one thing which is necessary. He has not demonstrated that there can only be a single necessary thing. Aquinas gives no reason to think that there might not be a multitude of necessary things which do not have their necessity caused, but rather exist necessarily in and of themselves. Certainly, if numerous such things were in existence, Aquinas would not say that the whole set of them is what is meant by the name, “God.”
Aquinas proposes an Argument from Gradation as his Fourth Way. He discusses the manner in which things are described, noting that some things exhibit a certain property to a greater or lesser scale than do others. He claims that this gradation is judged in comparison to some singular exhibitor which most exemplifies that property.
- There are some properties of things which can be accorded as greater or lesser.
- A property can only be accorded as greater or lesser as it resembles a thing which is the greatest exhibitor of that property.
- “Being,” “goodness,” and every other perfection can be accorded as greater or lesser in a thing.
- Therefore, there must exist a greatest exhibitor of “being,” “goodness,” and every other perfection. (1, 2, 3)
The second premise of this argument is worse than just dubious. Indeed, it would seem to be glaringly false. In his own example supporting the premise, Aquinas states that “hotter” is judged in comparison to fire, which must be considered “hottest,” since it is the source of all heat– yet another antiquated and abandoned position which Aquinas acquired from Aristotle. However, it is now known that fire is not the source of all heat, and that there exist things which are far, far hotter than fire. Even more damning to this perspective, however, is that a person need not ever know anything of fire to know that a stone which had been left out in the sun is hotter than one left in the shade. Nor is it even clear that “hottest” is a notion which can be applied to any single, universal thing. The gradation of a property is not judged by comparison to the maximal extremes of that property, but rather by comparison to other things which exhibit that property. An oven is hotter than a refrigerator and a blast furnace is hotter, still, but these are all still exceptionally cold in comparison to the surface temperature of a star.
Finally, the Fifth Way is an Argument from Teleology. Aquinas claims that there exist things which lack intelligence, and which yet act to a purposeful end. This purpose, he claims, must be instilled into those things by an agent with intelligence.
- There exist things which lack intelligence and act for some purpose.
- A thing which lacks intelligence cannot act for a purpose unless it is directed to do so by a being with intelligence.
- Therefore, some intelligent being exists by whom all things which lack intelligence are directed to their purpose. (1, 2)
Once again, Aquinas’ formulation seems problematic. Firstly, it is not clear that things which lack intelligence are acting in accordance with some distinct purpose. His attempted justification for this point does not seem to really lend it much support. Aquinas claims that these things act “always, or nearly always, in the same way, to obtain the best result.” It is far from demonstrated that this is the case; however, even if it is, it does not follow that that their actions are therefore directed by an intelligent being. Aquinas simply asserts that this is so. Again, this would seem to be a function of the priest’s reliance upon Aristotle, and his ignorance of the physics which would be discovered centuries after his Summa. Furthermore, as with the Third Way, Aquinas gives no good reason to think that all of these natural, intelligence-lacking things must therefore be directed by a single entity, other than the earlier argument regarding Efficient Causation which has already been seen to be problematic. Even if his premises were true, Aquinas is not justified in this leap of logic. The planets, for example, might each be driven in their orbits by an intelligent being distinct from that driving any of the others, and neither of the first two premises would be violated. As before, it is doubtful Aquinas would agree that all intelligent beings are what is meant by the name, “God.”
The Five Ways of Thomas Aquinas’ Summa Theologica are, to be certain, an important part of the history of philosophy. However, their brilliance and validity are very often overstated by proponents. Aquinas’ views are mired in a foundation of the positions of Aristotelian physics which, though extremely influential in 13th and 14th Century Christendom, are now extremely antiquated and which have been abandoned by all serious scholarship. Even within that framework, however, his arguments are rather loosely proffered and lacking in rigor. Aquinas’ Five Ways do not exhibit the strength of argument with which they are commonly characterized. As such, the question of God’s existence does not seem to be quite so well founded as the Italian priest claimed.
Boxing Pythagoras 
Reblogged this on James' Ramblings and commented:
Reblogging for future reference.
Have you reviewed Ed Feser’s work? He seems to be regarded as the authority for modern formulations of Thomistic arguments.
I’ve heard this, but haven’t yet had the time to give Feser’s work a decent read. Perhaps I will jump it to the head of my ever growing queue of To Read books.
For example, “He has not demonstrated that there can only be a single necessary thing”
Aquinas does this later illustrating that the necessary being is pure actuality. Basically he argues that there cannot be two necessary beings to the degree that one being that is different from the other would possess a different characteristic and therefore would possess potentiality.
I’m recalling this from memory waiting in a parking lot but Fesar is an expert as referenced.
UPDATE: I listened to the podcasts I mentioned, wherein Dr. Feser (in conversation with Matt Fradd) discusses the mistakes which Richard Dawkins makes in discussing the Five Ways. I definitely agree with Dr. Feser on most of the points which he raises. My one point of disagreement comes in Dr. Feser’s discussion of the Fourth Way, but it’s possible that he addresses my particular concern in his other works, so I’ll refrain from discussing it (at the very least) until after I’ve read his Aquinas.
Fair enough. It’s possible that my geometer’s bias for the Euclidean form of rigor was showing through, there, since I would prefer to see such a thing established BEFORE it’s conclusion is expounded; but I do have to admit that it would be entirely unfair of me to hold the Summa Theologica to the form laid out by Euclid’s Elements.
That said, Aquinas’ Third Way still doesn’t make much sense to me. I see no reason to think that a thing’s having the potential to cease existing implies that there must therefore have been some point in time at which it did not exist. Furthermore, even if this is the case, his next point seems to stand in contradiction with itself. Aquinas says, “Therefore, if everything is possible not to be, then at one time there could have been nothing in existence.” However, if nothing is in existence, then the time at which nothing is in existence does not exist– therefore, it cannot be the case that “at one time,” a thing which exists, “there could have been nothing in existence.”
Still, perhaps Dr. Feser’s Aquinas will elucidate on this apparent incoherency, as well.
The argument that I remembered off hand is one that Aquinas uses to argue against multiple Gods. These analogies are a more proper argument given for the contingency argument:
So, if you’re contingent on your parents, meaning that you exist because of them, we know that you’re contingent and not necessary because you would always have existed. As we observe this to be true, we know that you’re a possible being.
Now, Aquinas does admit there can be more than one necessary ‘being’ that is not God. So, for example, if one argues that matter has always existed it doesn’t negate the argument of Aquinas for God being the necessary being. The analogy given in this regard is to imagine that the sun which gives light to our planet has always existed. In this exercise, for our existence it is a necessary being, now the light from the sun also always exists, so it would also be a necessary being but yet the light is still dependent on the sun.
So, the two analogies establish the difference between possible and necessary beings. A possible being only comes to exist through an already existing cause that is external to it, if everything were possible being, there’d be no explanation how a possible being came into existence.
I think what you’re tripping up on is the second way which rules out that something can’t be the efficient cause of itself as you write, “2. No change can be its own Efficient Cause.” Now you critique the non-infinite chain claim of Aquinas, did Feser give the chandelier analogy in the podcast?
At any rate, I found Aquinas’ third way the most convincing, although Feser’s modern version of the 5th way with protons is very interesting.
Atlas, my collegiate training is in historiography, I merely dabble in Classical philosophy, so Feser’s book Five Proofs of God is most likely the best answer to your challenges.
Thanks for your continued commentary! I’m definitely enjoying the provocation to thought.
I can agree with this, given the framework of Time under which Aquinas understood the world. However, this isn’t really what I object to in the Third Way. Rather, I was objecting to the idea that something having the potential to cease existing implies that there must have been a time in which that thing did not exist.
He did not, but would I be correct to presume that this chandelier is meant to illustrate an essentially ordered series? If so, I can certainly agree that some essentially ordered series require a prime efficient cause, but I see no reason to think that all essentially ordered series necessitate such a condition. However, I should note that I certainly do not share Aristotle’s rejection of actual infinites, as Aquinas did, so that may be a large part of my disagreement, here.
I just started in on Feser’s Aquinas yesterday. I’m hoping that it helps. I’ll try to get to Five Proofs, eventually.
Thanks for your reply, all good points. Sorry but for some reason WordPress didn’t alert me to your reply. But these are good critiques and issuers rooted in finding the truth. Thanks for the challenging thinking.
One of Feser’s emphasis, as well as many Thomists, is that reading the five ways in isolation from the rest of the body of work of the Summa leads misreadings on Aquinas’ arguments.
I’ve just downloaded a couple podcasts in which Feser addresses Dawkins’ handling of the Five Ways. I’ll see what he says, there, and I’ve also got Feser’s Aquinas book at the top of my reading list, now. If he addresses any of my positions, or if it becomes clear that I’ve misunderstood one of Aquinas’ positions, I’ll be sure to revise. Thanks!
I’m with you on this Boxing Pythagoras, in that I too see no reason to think that a thing’s having the potential to cease existing implies that there must therefore have been some point in time at which it did not exist. But maybe it’s better to focus on what this premise seems to be getting at, which is necessity and possibility—in which case we should ask what sense of “possibility” is being invoked here? Logical possibility? Metaphysical possibility? Something else? The relevant meaning being appealed to here might hold differential implications for the argument.
I’m also reminded of John Heil’s piece (Ch. 10) in The Puzzle of Existence, which deals with necessity and contingency.
My understanding is the assertion hinges on potentiality. If something “changes,” it precludes that something cannot have always existed because the necessary being is pure actuality and it’s essence is existence itself.
Feser, as well as Matt Fradd, examine this more deeply. Feser’s book and Fradd’s book “Does God Exist?” And pinpoints outside is the five ways where Aquinas makes these arguments.
I’d also add that if Dr. Feser argument doesn’t convince one then my explanation of his argument is going to do any good either.
Cheers!
Philip, thank you for your reply. I have read some of Feser’s work, but I’m ultimately not convinced of his conclusions. Also, unless I’m mistaken, the notion of “change” being used here seems to invoke the A Theory of time, which we seem to have good reason to doubt given relativity. But even if that were not the case, it seems to me that the gap problem looms large here (I’ve spoken with Fradd about this as well, but I don’t think we got far).
I’d be interesting to hear that discussion. The way I see it is that discussing such theories in philosophy helps sharpen truth. Some folks get bogged down by their position; however, Boxing Pythagoras asks a question that honestly most Thomists take for granted including myself. When the position is presented—why does something ending preclude it beginning— doesn’t mean I’m, or anyone, convinced but rather develop a better understanding. It’s also not to say that Boxing Pythagoras raises a question that hasn’t been fully addressed.
Also, for Boxing and Philo, Fradd’s newest Podcast on Pints with Aquinas is on our discussion here. I haven’t listened to it yet but will plan so.
Good Day!
I downloaded the latest Pints with Aquinas, and I’ll give a fair listen to it later, but between reading Feser and listening to some of his discussions with other philosopher’s, it seems apparent that there are at least two major differences in our views of metaphysics which will likely prevent any of Aquinas’ work from being very convincing to me.
The first is, as I mentioned earlier, that I see no reason to think– as did Aquinas and Aristotle before him– that the existence of an actual infinite is metaphysically impossible.
The second, however, is much deeper and more problematic. As Philo intimated, Aquinas’ metaphysical foundation seems to be grounded in a Tensed Theory of Time (also called the A-Theory). The whole dichotomy of act and potential is necessarily grounded in such a view. However, as Philo mentioned and as I’ve stated in several of my articles before, we have very good reason to doubt that a Tensed Theory of Time is true, as well as very good reason to believe that a Tenseless Theory (or B-Theory) is true. If you’re interested in learning more about that, I’d recommend my series of articles called “WLC on Time.”
Given that there is such a massive difference in our views of metaphysics, I’m not sure it’s really worthwhile for me to critique Aquinas any more than I have. It’d be like critiquing Ptolemy’s Almagest using data from WMAP.
Thanks for pointing that out Phil. I haven’t listened to Fradd’s podcasts in a while. For me, I think the difficulty is twofold: the first, similar to Boxing Pythagoras, relates to the metaphysics of time seemingly invoked by the argument. But the bigger problem, in my view at least, is that it’s not always clear what sense of necessity is being invoked, and yet this is important to clarify if the argument is to be subjected to evaluation.
There’s an introductory philosophy text from the 80s’ that highlights this point well (unfortunately I’ve forgotten the names of the authors’)—it points out that if logical possibility is used in one premise but metaphysical possibility in another, then the argument equivocates on “possibility” and thus cannot succeed. This is why I think other versions of the cosmological argument, like those advanced by Leibniz and Clarke, are to be preferred; their clarity better lends them to examination.
The greatest virtue of cosmological arguments, in my opinion, isn’t that they succeed in establishing the existence of God (in my view, they don’t), but that they point us toward the deeper question of why there is something rather than nothing. Ultimately, other considerations might lead us to conclude that such a question doesn’t make sense to ask—that it is ill-conceived, as Adolf Grunbaum, among others, argues. But even that would be a significant philosophical triumph in my books.
Please, watch the videos presented by Joseph Schmid refuting Aquinas First and Third ways. Go in Youtube and type “Majesty of Reason, First Way: An Analysis.” This video is extremely sophisticated and interesting! 🙂
This is a very dishonest presentation—let alone “analysis”—of the Ways. It falsely claims that various premises receive “absolutely no justification”, when in fact Aquinas dedicates an extensive portion of the Summa to justifying them. Whether you agree with the justifications or not is besides the point. Pretending he never made them is the problem: It is lying, plain and simple.
Did you actually read the Summa, or did you base your “analysis” off some summary you found on Wikipedia or elsewhere online? That is, was this done accidentally or deliberately?
If I am mistaken in my discussion of Aquinas, I am honestly mistaken. I have no intent to obfuscate, hide, or ignore any of his arguments or work.
Where in the Summa do you find my objections answered or justifications offered for the specific premises which I call out here? I’d be more than happy to discuss these and if I am in error I would appreciate the opportunity to correct my mistakes.
I will admit that, when I first wrote this article, I had only read the specific excerpt which I am addressing– that is, Volume I, Question 2, Article 3, which is commonly known as Aquinas’ Five Ways. Even now, I will fully admit that I have not read Volumes II through V of the Summa, though I have read the rest of Volume I. Are the answers to my objections found somewhere in those volumes? If so, where?