Feser’s 5th proof is the ironically titled rationalist proof.
Common sense and science alike suppose that there are explanations for the existence of the things we encounter, the attributes things exhibit, and the events that occur. And typically we find that this is indeed the case.
Yes, things within our experience tend to have causes. However
We can’t extrapolate that to things outside of space and time.
Our experience shows that causes are physical, which if true, would rule out god.
Our experience also shows that causes are not omnipotent.
Causality can plausible be a relationship between spatio temporal events.
But does everything in fact have an explanation, even if it’s an explanation we haven’t discovered and never will discover? The thesis that this is the case is known as the principle of sufficient reason, or P SR for short.
We have no good reason to suppose the PSR holds outside of spacetime. It’s hard to find a sufficient explanation for the first thing, which caused other things or for the infinite causal chain.
Why should we believe PSR? One important argument for it is a variation on the empirical argument for the principle o f causality we considered in chapter 1. Considered as an inductive generalization, P SR is as well supported as any other.
But there are lots of other similar generalizations. The non omnipotent caused generalization is also inductively well supported. A few more problems plausible present themselves.
This likely leads to modal collapse. If everything has a sufficient explanation, then things can’t be different from how they actually are.
There’s no sufficient reason for god’s existence.
If god is omnipotent he can plausibly stop existing, but if he’s necessary he can’t, as Sobel argues.
Also, if there are contingent things, then that means that they can’t rely on necessities. Contingency requires that things are not logically entailed by necessary things, which refutes the PSR. This is also argued by Sobel.
For if P S R is false, then there might be no reason whatsoever for our having the perceptual experiences we have. In particular, there might be no connection at all between our perceptual experiences and the external objects and events we suppose cause them.
This is false—positing that there is an explanation of our perceptual experiences doesn’t require positing that everything has an explanation for its existence. All that is required is positing that there is an explanation for the set of things which includes our perceptual experience, which can be done by positing that every physical thing has a physical cause.
There is another way in which science in particular implicitly presupposes PSR. Some philosophers have taken the view that there can be genuine explanations, including scientific explanations, even if P SR is false. One finds such a view in J.L . Mackie and Bertrand Russell.6 The idea is that we can explain at least some phenomena in terms o f laws of nature, those laws in terms of more fundamental laws, and perhaps these in turn o f some most fundamental level of laws. The most fundamental laws would, however, lack any explanation. That the world is governed by them would just be an unintelligible “brute fact” . But this is incoherent. Suppose I told you that the fact that a certain book has not fallen to the ground is explained by the fact that it is resting on a certain shelf, but that the fact that the shelf itself has not fallen to the ground has no explanation at all but is an unintelligible brute fact. Have I really explained the position of the book? It is hard to see how. For the shelf has in itself no tendency to stay aloft— it is, by hypothesis, just a brute fact that it does so.
There’s no reason brute facts are unintelligible. Feser just throws in the word unintelligible into the explanation in an attempt to sneak in incoherence. It may not be an ultimate explanation, but it’s as far as explanations go. The fundamental explanation of the ultimate laws may be “that’s just the way things are, stop asking questions.” While that may be unsatisfying to Feser, science isn’t determined by the whims of aristotelians. We cannot demand a deeper explanation than the one presented by reason.
Informal statement o f the argument: Stage 2 Why should we think o f the necessary being as God? Consider first that, from the fact that it is necessary, it follows that it exists in a purely actual way, rather than by virtue o f having potentialities that need to be actualized.
This was responded to previously. Additionally, mathematical truths are plausibly necessary but they are not purely actual and certainly not omnipotent!!
N ow we saw in earlier chapters that there cannot even in principle be more than one thing which is purely actual, absolutely simple, or subsistent existence itself. Hence, if we begin with the existence o f the collection o f contingent things and reason to a necessary being as its cause, we know that there is only one such necessary being. Or, if we begin with the question o f what keeps some particular contingent thing in existence at any moment, and reason to a necessary being as its cause— and then go on to note that every other contingent thing will, for the same reason, have to have a necessary being as its sustaining cause at any moment— then since there can only be one necessary being, we know that it is the same one necessary being that is the cause o f all contingent beings. Furthermore, since this necessary being is unique in this way, and the only other things there are are contingent things— all o f which, again, are caused by the necessary being— we can infer that this necessary being is the cause of everything other than itself.
We’ve already seen why such arguments fail. There are lots of necessary things like mathematical, moral, and modal truths that don’t plausibly depend on this necessary being. Even if it’s changeless and necessary, that doesn’t entail the other properties.
God isn’t necessary because we can imagine a world without god. We could imagine any number of universes without a god, such as a universe that’s simply zero dimensional points bouncing around, or a lifeless universe, or even a vibrant universe filled with life. If god is necessary then he would have to exist in that universe, the same way that 1+1 would still = 2 in that universe, and yet the possibility of his nonexistence proves that god isn’t necessary. For this argument to succeed nothing existing has to be logically impossible.
Closing thoughts on Feser
Feser’s arguments are not effective. They derive their apparent force from relying on hard to understand aristotelian jargon. Once unpacked, the premises are clearly faulty.
Your attempt to rebut the argument from empirical skepticism is patently circular, as it depends on inferring something from experience; yet this only provides a good reason to think the relevant claim is true insofar as such experiences are caused (reason to suspect a deviant causal chain w.r.t. one's experiences are frequently taken to be defeaters in the literature; a fortiori *uncaused* experiences), which is precisely what is at issue.
Nor could you attempt to avoid this by saying you know all physical things have physical causes a priori, for (a) you obviously cannot hold that to be a necessary / a priori truth, especially given your commitment to the thesis that contingency is insufficient to infer causal explicability a priori; and (b) you don't know your perceptual experiences are physically constituted a priori.