Ever since discovering Aquinas’ third way, Copleston’s cosmological argument (in his debate with Russell), and reading Pope Pius XII’s statement in Humani Generis that:
It is well known how highly the Church regards human reason, for it falls to reason to demonstrate with certainty the existence of God, personal and one; to prove beyond doubt from divine signs the very foundations of the Christian faith; to express properly the law which the Creator has imprinted in the hearts of men; and finally to attain to some notion, indeed a very fruitful notion, of mysteries. But reason can perform these functions safely and well only when properly trained, that is, when imbued with that sound philosophy which has long been, as it were, a patrimony handed down by earlier Christian ages, and which moreover possesses an authority of an even higher order, since the Teaching Authority of the Church, in the light of divine revelation itself, has weighed its fundamental tenets, which have been elaborated and defined little by little by men of great genius. For this philosophy, acknowledged and accepted by the Church, safeguards the genuine validity of human knowledge, the unshakable metaphysical principles of sufficient reason, causality, and finality, and finally the mind’s ability to attain certain and unchangeable truth.
I have never been able to shake the sense of rationalistic romance the PSR elicits in me. I often feel as though, when the principle is criticized (however cleverly), I am more certain that the principle is sound then I am that the arguments against it are sound (a Moore-ian response), in the same way as I’m more certain about libertarian freedom than I am any of the clever arguments against it. However, since love is blind, and since to some extent a lot is at stake (if not the existence of God, or even it’s demonstrability, at least the Catholic faith as propounded by the Ordinary Magisterium which binds Catholics to believe in God’s demonstrability by, among other things, the principle of sufficient reason; not to mention my rationalistic tendencies), perhaps I am wrong to hold onto the PSR in light of criticisms. Maybe I need to adopt a weaker more modest version of the principle, strong enough to demonstrate the existence of God, and weak enough not to run into the alleged problems of modal collapse et al. What kind of principle could satisfy this? What is interesting is that, I think, that very line of inquiry leads right to an extremely plausible argument for the existence of God which is (almost) necessarily more plausible than EVERY cosmological argument for the existence of God.
Let’s say that the Principle of Sufficient Reason should be construed the way it is most often construed, namely as that “every contingently true proposition has some explanation of it’s being true.” This, we are told, is too strong, because it seems to imply modal collapse altogether and would be, therefore, self-defeating (or trivially true).
Suppose for the sake of argument, then, that we say that the PSR is dubious, since some formidable challenges to it can be, and are, posed. We may opt, therefore, for a weakened principle, maybe something like this: “every fact which logically possibly has an explanation does have an explanation” (inspired in part by Pruss & Gale, as well as by Timothy O’Connor). This principle may exempt certain libertarian facts from requiring explanation in the strictest sense (and perhaps allow that to the extent that these facts can be explained, they must be). This principle, though, demonstrably demonstrates the existence of God as well (see this paper, and this one). In passing we might note that perhaps Molinism can be purchased with such a weakened principle, given the law of excluded middle and the ‘plausible’ intelligibility of subjunctive counterfactuals of creaturely freedom, and the A-theory of time could still not be preferred to the B-theory, because the A-theory allows for no explanation of why it is ‘now’ whatever time it is, the B-theory can explain this, and therefore it is logically possibly explained unless the B-theory is logically impossible.
Maybe this weakened principle of sufficient reason is still objectionable for some clever reason. Maybe, then, we ‘weaken’ it further (or differently). We can construe it as a metaphysical, rather than a modal, principle. So the Metaphysical Principle of Sufficient Reason (MPSR) says that “every contingent being which exist has been caused to exist by another being.” So long as we can make the whole contingent world out to be one contingent being, the MPSR is strong enough to obviate Theism. I note that Pope Pius actually called the principle a ‘Metaphysical’ Principle of Sufficient Reason, though I think it may be a mistake to read too much into that. This may be open to objections as well though, such as Russell’s objection given his view that “a subject named can never be meaningfully said to exist.” So that the world, for Russell, cannot coherently be said to exist.
So, we weaken the principle further to something like “out of nothing, nothing comes, and therefore anything which exists contingently comes out of something” (one needs to be careful not to slip into linguistic traps here, since ‘come out of’ is being used here in a very odd eclectic sense). This principle, which is really just a logical elaboration of the ex nihilo nihil fit, seems to get us to God as well. I’ll assume that there may be some clever objection to this too.
Maybe we weaken the principle further, therefore, to something like this: “for any contingent being or set of beings, it is more plausible than not that such beings were brought into existence by at least one other being.” Again this principle will lead us straight to an incontingent being with the ability to bring the whole aggregate of contingent beings into existence, and this incontingent being will more plausibly exist than not.
Maybe we weaken the principle further, making it an epistemological principle stating that “if some fact has some possible explanation, then it is unjustifiable [Ceteris Paribus?] to maintain that it does not have an explanation” which may give us a good reason to think that if God can possibly serve as an explanation for the world (and is the only available option in this cosmological-case) then Atheism and Agnosticism are unjustified.
Let’s assume we continue to enumerate various different principles of sufficient reason, and let’s assume for the sake of argument that each one can be plugged into an argument which validly leads to the conclusion that God exists (and which would be ‘sound’ just in case the principle were correct). Now, surely the weakest versions of these principles, being less objectionable than their stronger peers, will seem more plausible than their peers, and (I think obviously) more plausible than not. Now we must ask the following question: is it more plausible that every single one of these principles is wrong, or that at least one of these principles is right? If the later is more plausible all things considered, then all things considered Theism is not just a rationally tenable conclusion; failure to assent to Theism appears unjustified since it appeals tacitly to the position which is less plausible. However plausible any one of the principles are, this argument will be at least as plausible, and, unless no principle other than a single (extremely weak) one is plausible at all, it will follow that this argument just combines the plausibility of ALL cosmological arguments, and so inherits a greater plausibility than any one argument.