Thomas Aquinas: the Fifth Way. Is Aquinas correct?


STT, I’m sorry, but I don’t follow what you’re saying. What do you mean “because of miniature inside the acorn?”


I don’t think English is his first language. He probably means the seed


Well, that’s really what we’re referencing. I suppose saying “acorn” is like referring to a chicken egg (including shell, white, and yolk), even though there is the fertilized egg inside, which is what the being in question really is. But we just end up with the same example here, where instead of saying the acorn has its end in the oak tree, we have the seed-within-the-acorn has its end in the oak tree.


I mean, because of the DNA and the way that cells are structured inside acorn.


We need not regress to this level, but sure, why not?

Why does DNA exhibit the teleology it does as opposed to some other teleology or none?


DNA is simply made of elementary particles. Elementary particles to the best of our knowledge follows laws of nature. DNA exhibits an specific teleology because of the way the particles are structured within.


Well, why do the particles within behave the way they do? And please define for me what a “law of nature” actually is.


Either the particles has structure or not. We fall in trap of infinite regress in the first case. In the second case, we face a brute fact, the particles have a set of attributes which dictates how they should behave.

Laws of nature is simply a set of identities which acts as constraints between a set of variables. For example the second law of Newton express a constrain between mass, acceleration and force (each being a variable).


“Particles behave the ways they behave because that’s how they behave.”

Aquinas’ point is that the “ends” of these particles must in some way be present. Say X particle behaves in Y manner under Z conditions. Take away all Z conditions and all X particles behaving in Y manner. X particles still have the potential to exhibit Y behavior. That is, the X particle still has Y as one of its targets or ends. The end “Y” still exists in some manner if it’s something that can be attained by X. But it doesn’t exist in the X particle that has not yet attained X, otherwise we’d have a contradiction: both X has not attained Y and X has attained Y. That doesn’t make sense. So, if the end exists in some manner, where is it?

(And furthermore, we run into an issue where we must address why one set of behaviors applies and not another, but that’s an argument from composition, not the Fifth Way, so we can disregard this.)

Actually, I think this will be the more interesting part of the discussion, but I’m not sure you’ve given me an answer. I mean, what do you mean by a “set of identities?” Perhaps that’s not entirely clear, though, because I certainly understand what’s meant mathematically. What I’m trying to ask you is this: Does this set of identities or law of nature exist in itself as a real feature of reality? Or is this simply a manner of describing the behavior of other real things?

Or to better illustrate the difference, do things behave in a certain way because of a law of nature (external to the things behaving)? Or do they behave in a certain way because it’s in their nature to behave a certain way (and what we call laws are just descriptions of this)?


Here’s another article which might help clarify the Fifth Way.


By what standard do you determine something to be a brute fact? Brute facts are completely arbitrary. You cannot reason to a metaphysical brute fact. Brute facts are an affront to reason itself since it denies that there is a reason for something.


Thanks a lot for this article, I just have one question that is not adressed there. Do the laws of physics/nature or entrophy somehow contradict with the “everything acts for an end” statement. It seems to be a thing people often use against Thomas.


IWantGod brought up a similar concern earlier. No, they don’t contradict the idea that everything acts for an end. Appealing to a “Law of Nature” is a vague thing in itself. What exactly do they mean? For one, is the person appealing to Laws of Nature stating that these things are real outside of any other material/energy objects? If so, that’s a very Platonic take on reality. It’s not really compatible with nominalism or conceptualism, and seems to have to be at least a Platonic realism. Then you could engage in a debate with the Platonist and compare with Aristotelian or Scholastic realism. Even if it’s Platonist realism, why does the Law of Nature, which is a real thing in itself in such a scheme, directed towards the end it is and not some other end? How is it directed towards any end at all? If instead Laws of Nature are not real things in themselves but is only our way of describing how things regularly behave, we’re still left with the same concern about why non-intellectual things are still directed to the ends they are.

If the person instead objects that it’s just an ontological brute fact, well, that seems rather adhoc, no? It certainly doesn’t conform to the principle of sufficient reason, and if the most fundamental realities of reality don’t have a reason, that’s like a tower of cards without any bottom layer of cards on the desk. If X is explainable only in reference to Y, but Y is unexplainable, then ultimately X is unexplainable. And even just going back to brute facts, is it really more plausible to go with something un-explanatory than something that is self-explanatory? What motivation is there to stop the logical inquiry there?



The idea of the “laws of nature” is a Biblical analogy: just like God placed law onto Israel, God placed law onto nature.

On the other hand, St. Thomas conceives nature as an interior, norishing source within things from which a thing’s various abilities stem.

Both see nature as acting for an end, but one sees this as extristic to the thing, while the other sees this as arising from within the thing itself.

But we can bring the two views together as Catholics, through the approach of infusion: nature is a Divine logos infused into a thing. In this way, nature is both a source, and a result of something transcending it.

Christi pax.


What do you mean with conditions? If you mean “the state of something” then you cannot take away all Z conditions since the system become ill-defined.

Moreover X reach Y as a result of behavior of X under condition Z but Y does not ontologically exist. The only thing which exists is X.

The particles are not intelligent therefore there exist a unique set of identities which describe their behavior. That is brute fact. Why they behave in this way rather than that way? Because of their nature, their attributes.

The second one. Laws of nature simply is a way of describing the behavior of the particles.

The second one. Things behaves in certain way because of their nature.


That is correct. Metaphysics is a set of brute facts but there exist not any metaphysics if there is no underlying reality. What exists is only physics which is a set of brute facts and describes reality.


How can X attain Y if “X attaining Y” is not an end that is real in some fashion? If it isn’t real in some way, it’s not attainable. Even if we’re looking at current conditions as opposed to future conditions, if X is in state A given the current conditions, why is it within state A instead of B or C? How can it determine itself to A? And if it’s possible to not be in state A, then X attaining A is only possible, but would remain a possible end, a real end in some way, even if no X is currently attaining A.

I agree that they tend towards certain ends because it’s in their nature to do so, but that doesn’t establish why it tends towards end A and not ends B, C, or D, or how it can direct itself towards certain ends being a non-intelligent thing. You also assert that it just is brute fact. Do you have any demonstration that this is true or rational? Or is your reason for declaring it brute fact as unexplainable as the brute fact?

Good. You agree with the Aristotlean on that. That was important to get out of the way. However, your appeal to “Laws of Nature” is rather useless, then. If it’s not governed by external laws of nature, then it’s governed by its own intrinsic rule set. It’s in the nature of X to tend towards Y. No need to throw in the term “law of nature”.

A scholastic understanding of metaphysics and physics does not depend on any unexplainable, ontological brute facts. If a thing is has properties that require explanation extrinsic to itself, it has an explanation.

Please provide a proof of how “what exists is only physics which is a set of brute facts.” Also, you contradicted yourself. You earlier stated that laws of nature don’t exist as real things in themselves. Things don’t tend to certain ends because of physics, physics is just a descriptor of the natures of things. So an appeal to “physics” as brute fact is again muddying the waters here. If what you said before is true, physics does not exist and is not a set of brute facts. What you should be claiming, to be consistent, is that “things exist which have brute fact natures that explain their ends and tendencies.” No? I haven’t thought about this reformulation exhaustively, but it certainly seems closer to the mark than claiming “physics exists” (as if it were a being of its own) if you earlier denied that it doesn’t. Even if we’re clear on what we’re talking about when you use the term physics in carefully defined circumstances, other readers might not, and even so, we probably want to be careful how we use the term in this discussion lest we start speaking as if it’s a collection of Platonic Forms accidentally or out of habit.

In addition to that, please provide a demonstration of how we can know what is a brute fact and what isn’t? Why is A unexplainable but B requires explanation? Why presume that anything requires explanation, or how we can know that any particular thing requires explanation?


What I mean is that X is a being but Y is not a being. Is Y more than a set of attributes of X?

The fact that the end is unique is related to fact that the particles are not intelligent. Why A, rather than B, C or D? That is brute fact if there is no underlying reality. This is explained better in the next comment.

That I have already argued about. The particles, lets call them P1, either have structure, other core particles, lets call them P2, and the core particles have structure too, etc. or they don’t. This means that the behavior of P1 is explicable in term of P2, etc. We however cannot go to infinity in the number of core structures so the core structure should have an end at certain point, lets call the related particles to be Pn. The behavior of Pn is just related to nature of them since there is no underlying structure anymore.

X tends towards Y because X has motion. And X has motion because of nature of X yet Y is not more than an attribute of X. What would be next Y given previous Y? That is laws of nature which dictates that.

Metaphysics is physics if there is no underlying reality. So we are facing brute facts in level of metaphysics or physics depending on whether there is an underlying reality or not.

I didn’t say so. I said physics, which explain the behavior of the particles, is a set of brute fact if there is no underlying reality, other core particles for example or completely a different reality.

Laws of nature are not real being but real thing. That is what I meant.

Beings either in core behave unintelligently or intelligently. We are dealing with brute fact in the core when beings are unintelligible. This means that there exist a set of identities, laws of nature, which uniquely explain the behavior of beings, unless we are living in a chaotic world.


X tends towards Y. X having attained Y might not exist physically, but it must exist in some way if X can be said to be tending towards it. This existence cannot only be physical, because even if there is no physical existence of X having attained Y, X still tends towards Y. So it must exist in some other manner.

I also agree that we cannot have an infinite regress in this type of series. That is part of the point of the argument. It must terminate at some point. The problem with a brute fact is that it requires stating that there is no explanation. “There is no reason why X tends towards Y instead of A, B, or C, it just does.” How is this a satisfactory answer? What motivation is there for terminating a series in an arbitrary way that undermines causal relationships for all of reality?

Perhaps it’s just the language, but you speak of the “laws of nature” as if they have intelligence. Things have rule sets according to their nature, but something non-intelligent cannot obey rules. Nor can they direct themselves towards their ends.

The discussion is that there must be an underlying reality, that is, God, for things to be explainable as they are.

You are begging the question. Please prove that there are ontological brute facts, or at least that it is plausible or rational. You state it with such surety.

You say that laws of nature must be brute facts unless we are living in a chaotic world, but the point is that any assumption of ontological brute facts undermines belief in an orderly world, because you are ultimately claiming that reality is governed by unexplained, uncaused, brute facts (which again, begs the question). If the explanation for everything else refers t these laws, and these laws do not have explanation, then nothing has explanation.

Furthermore, you do not have a sufficient reason to distinguish between what is a brute fact and what is not. Why and how do you make such a distinction in a way that is not arbitrary?


I think the nature of the particles dictates the end Y instead of A, B or C. Having another sort of particles leads to another end. At the end the only important things is that the end is unique (unless the underlying reality is intelligent).

The motion of particles is non-intelligent because their motion can be predicted. Motion is the result of force which force is the result of existence of particles in a field generated by other particles. That is one interpretation. The other interpretation is that the particles experience the field and act accordingly. The last interpretation is that God holds things at motion. For that however God needs to know our decision at instance. This somehow embed God in time. I am amused with eternal act. I cannot understand how it could turn into a proper temporal act, to sustain everything.

I already argue against this picture (previous comment).

We already agree that the underlying reality cannot have infinite structures. So it exist an underlying reality which behave as a result brute facts. The brute facts cannot be explained. They are principles. Physics is not closed yet, standard model is not anomaly free, therefore there is an underlying reality. So we still don’t have the theory.

Yes, what you said is right until the last part (bold part). Things in higher level have explanation in term of things, brute facts, in lower level.

We have to dig the reality we observe until the edge, when we face brute facts.

DISCLAIMER: The views and opinions expressed in these forums do not necessarily reflect those of Catholic Answers. For official apologetics resources please visit