Tuesday, August 20, 2019

Why the Five Ways don't prove the existence of five (or more!) deities

Here is a potential problem for Aquinas’ Five Ways. Each of them proves the existence of a very special being. But do they each prove the existence of the same being?

After giving the Five Ways in Summa Theologica I, Aquinas goes on to argue that the being he proved the existence of has the attributes that are needed for it to be the God of Western monotheism. But the problem now is this: What if the attributes are not all the attributes of the same being? What if, say, the being proved with the Fourth Way is good but not simple, while the being proved with the First Way is simple but not good?

I now think I see how Aquinas avoids the multiplicity problem. He does this by not relying on Ways 3–5 in his arguments for the attributes of God, even when doing so would make the argument much simpler. An excellent example is Question 6, Article 1, “Whether God is good?” Since the conclusion of the Fourth Way is that there is a maximally good being, it would have been trivial for Aquinas to just give a back-reference to the Fourth Way. But instead Thomas gives a compressed but complex argument that “the first effective cause of all things” must be desirable and hence good. In doing so, Aquinas is working not with the Fourth Way, but the Second Way, the argument from efficient causes.

Admittedly, at other times, as in his arguments for simplicity, St. Thomas relies on God not having any potentiality, something that comes directly from the First Way’s prime mover argument.

This reduces the specter of the attributes being scattered between five beings, corresponding to the Five Ways, to a worry about the attributes being scattered between two beings, corresponding to the First and Second Ways. But the First and Second Ways are probably too closely logically connected for the latter to be a serious worry. The First Way shows that there is a being that is first in the order of the actualizing of the potentiality for change, an unchanged changer, a prime mover. The Second Way shows that there is a being that is first in the order of efficient causation. But to actualize the potentiality for change is a form of efficient causation. Thus, the first being in the order of efficient causation will also be a prime mover. So there is a simple—so simple that I don’t recall Aquinas stating it in the Summa Theologica—argument from the conclusion of the Second Way to the same being satisfying the conclusion of the First Way.

Consequently, in the arguments for the attributes of God, Aquinas needs to only work with the conclusion of the Second Way, and all the attributes he establishes, he establishes as present in any being of the sort the Second Way talks about.

That still leaves a multiplicity problem within the scope of a single Way. What if there are multiple first efficient causes (one for earth, one for the moon, and so on, say)? Here Thomas has three solutions: any first being has to be utterly simple, and only one being can be that on metaphysical grounds; any being that is pure actuality has to be perfect, and only one being can be that; and the world has a unity and harmony that requires a unified first cause rather than a plurality of first causes.

Finally, when all the attributes of God have been established, we can—though Aquinas apparently does not, perhaps because he thinks it’s too easy?—come back to Ways Three through Five and ask whether the being established by these ways is that same one God? The ultimate orderers of the world in the Fifth Way are surely to be identified with the first cause of the Second Way once that first cause is shown to be one, perfect, intelligent, and cause of all other than himself. Plausibly, the maximally good being of the Fourth Way has to be perfect, and Aquinas has given us an argument that there is only one perfect being. Finally, the being in the conclusion of the Third Way is also a first cause, and hence all that has been said about the conclusion of the Second Way applies there. So, Aquinas has the resources to solve the multiplicity problem.

All this leaves an interesting question. As I read the text, the Second Way is central, and Aquinas’ subsequent natural theology in the Summa Theologica tries to show that every being that can satisfy the conclusion of the Second Way has the standard attributes of God and there is only one such being. But could Aquinas have started with the Third Way, or the Fourth, or the Fifth, instead of the First and Second, in the arguments for the divine attributes? Would doing so be easier or harder?


Brandon said...

If we go through the major attributes, we get:

Q3.1 Incorporeal: First Way, Fourth Way (most noble)
Q3.7 Simple: Second Way, First Way (potency and act), Fourth Way (absolute being)
Q4.1 Perfect: Second Way
Q6.1 Good: Second Way

Many of the other attributes are derived from these, so the First and Fourth Ways are already in the mix as supplementary sources. I think this interweaving becomes even more obvious in the Summa Contra Gentiles. So these seem to be ones that you could straightforward pull out as your primary emphasis.

People forget that the Third Way, as Aquinas actually presents it rather than as it is usually reconstructed, includes the Second Way as one of its branches: its conclusion is that there must be a necessary (in the sense of ingenerable & imperishable) being and this is either something necessary in itself or an effect to which one would apply the Second Way to get a first cause, which given the effect would have to be necessary in itself.

The Fifth Way is an interesting question; Aquinas only very rarely appeals to it. I wonder if one can argue that this is because it would be the hardest to use.

Michael Gonzalez said...

I am not sufficiently familiar with the 5 ways to comment on that, but I have noticed an interesting fact in thinking through an Ontological+Leibnizean sort of argument:

1) Any necessary concrete entity will need to be omnipotent. (In the possible worlds where an omnipotent being exists, all other beings rely on that one to continue existing; the necessary being cannot rely on any other being; so in the possible worlds where there is an omnipotent being it is one and the same as the necessary one).
2) There cannot be more than one omnipotent being. (Reliance again).
3) Therefore there can only be one necessary concrete being. A result is that, if one separately runs a moral argument to the existence of a necessary and perfectly good being, it must be the very same being as the omnipotent one, and the same as the explanatory ultimate argued for in the Leibnizean style.

The most interesting part for me has been to see how ontological and Leibnizean (and "unrealized possibility") arguments really reduce to some core conceptual issues. It's been very illuminating to pick apart. For example: What does it mean for something to exist necessarily? It seems to me that the key point will be that it has no necessary or sufficient conditions (thus, any state of affairs will satisfy the necessary and sufficient conditions for this being, and it will exist). So, as long as it can be non-contradictorily necessary (i.e. no contradiction is entailed, such as trying to posit a being that takes up space or is composed of matter, etc., but saying it has no conditions) it is actually necessary. The key is for it not to require anything. The main remaining argument I struggled with was "what about the empty possible world", and the answer (I think) is to ask "is this being still possible in that world?" If so then, given a "powers" approach to modality, such a world is a self-contradiction. A thing is possible just if it either exists or it is within the powers of things that do exist to bring it about. This Being cannot be brought about as it has no conditions, so it can only be possible when it is actual. And, given that an otherwise empty world still meets all of its necessary and sufficient conditions for existing, it will exist. This fits well with the fact that this thing is the ultimate explanation why anything is possible anyway (which fits with omnipotence, etc).

The other argument was "but a perfectly good Being can't instantiate bad worlds". The answer to that one seems easy to me: It has sufficient power to bring about such worlds; and that's all that's needed for possibility. Not that it every would bring about such worlds.

Anyway. I don't mean to hijack the post; it's just been stirring around in my head for a while now, and this reminded me of it. I think Aquinas was on to some of these same intuitions, but he was much more sophisticated and eloquent in his presentation.

Alexander R Pruss said...


I missed 3.1. I am not sure 3.7 depends on the Fourth Way: the absolute being of God could also be derived from 3.1-3.6.

In any case, 3.1 forces me to modify my thesis: Aquinas occasionally uses ways other than one and two, but only one and two are *essential* to the line of argument.


In 1, where do you get the claim that if x is a necessary concrete being, then everything (or even anything) else depends on x?

Michael Gonzalez said...

Pruss: My reasoning was that, in a world where an omnipotent being exists, all other beings depend on that one for their continued existence; but a necessary being cannot depend on another in that way. So, since the necessary being will exist in all possible worlds, it follows that, in the possible worlds where omnipotence is instantiated, it must be instantiated by the necessary being itself (thus it is not dependent on any other being). Does that make sense?

Alexander R Pruss said...

Oh, I see: you assumed the ontological argument already proved the existence of at least omnipotent being.

I am still not convinced. Classical theism is OK with saying that it does not take away from omnipotence to be unable to do logically impossible things. Perhaps, similarly, it does not take away from omnipotence to not have other logically necessary beings depend on one?

Michael Gonzalez said...

Pruss: No no, I'm saying that if omnipotence is possible (instantiated in at least some possible worlds), then a necessary concrete entity (call it "G") will either be the omnipotent entity or else there would be a possible world in which G coexists with the omnipotent one and depends on that one for its continued existence.

To answer your response about logical impossibilities: I don't know if we can protect G from destruction by simply stipulating their necessity. I think we would need an account in terms of its powers or other properties. The problem with omnipotent beings performing logical impossibilities is that logical impossibilities are meaningless. But it is not meaningless to say that omnipotence (if possible) would mean having sufficient power to destroy anything and everything else.

Indulge me just a bit further and consider it from the other, Leibnizean sort of angle: the postulated necessary entity, "G", is the ultimate explanation for not only what is actual but also for what is possible (again, leaving aside meaningless strings of letters; i.e. logical contradictions). G's actual existence and powers are the ground for all that is and even could have been at the grandest and most fundamental scales (which already sounds like a decent definition of "omnipotence", with all the right limits and none of the wrong ones). It follows that, if omnipotence is possible, it is either instantiated in every possible world (and is thus the same as G, given (2)) or else it is contingently possible the same way anything is: because G has sufficient power to instantiate it... but that also makes G omnipotent.

Brandon said...


On the Fourth Way in 3.7, I was going on the fact that elsewhere in the question he associates the absolute being talk with participation, using the example of forms; and this would be related to the Fourth Way as it is often interpreted. But it's true that this goes beyond what is explicitly stated in the arguments themselves. But perhaps I could have pointed to 3.4 instead, which is key for getting to 3.7, and uses three arguments: one based on God as first efficient cause (thus bringing in the Second Way), one based on actuality and potentiality (which suggests the First Way), and one based on participation using the example of fire (which at least suggests the Fourth Way).