YOU might not expect an agnostic to have a favourite proof of God’s existence, but I have. It is not one that many people have heard of, possibly because not many people have heard of the person who devised it: the maverick French philosopher André-Pierre Le Guay de Prémontval (1716-64).
This is a shame, because the proof is ingenious. It tries to get atheists to accept that God exists, using a principle that they already accept: namely, that all existing beings are uncreated, and so exist in and of themselves, necessarily. Atheists of the 18th century typically believed this very thing.
Prémontval’s proof starts by trying to show that these atheists are, in fact, committed to a broader principle: that all possible beings exist necessarily. As these atheists are not explicitly aware that they are committed to this, the first part of Prémontval’s proof is designed to show them that they are so committed.
To understand how this part of the proof works, we need to know what is meant by a “possible being”. A being is said to be possible if we can conceive no contradiction in the idea of it, and impossible if we can conceive a contradiction (as we do in the idea of a square triangle, for example).
Now, 18th-century atheists happily acknowledged that there were countless possible beings, but said that only a tiny proportion of them actually existed. To be a little more precise: the atheists held that the possible beings that existed had the property of aseity (that is, the property of existing necessarily), while the ones that did not exist were devoid of this property.
Since these atheists would accept that some possible beings had the property of aseity, Prémontval reckoned that they should accept that all possible beings had it. He argued for this on the grounds that it would be absurd to think that some possible beings had this property (and so existed necessarily), while other ones did not have it (and so did not exist at all). After all, what explanation could atheists give why one possible being and not another had this property?
Once atheists realised that they could not offer an explanation, Prémontval thought that they would acknowledge that they were, in fact, committed to holding that all possible beings had the property of aseity, and so existed necessarily.
Prémontval then finished off his proof by noting that an omnipotent, omniscient, and perfectly good God must be among the infinite number of possible beings, as the idea of such a being contained no contradiction. And, since God was a possible being, it followed that God — along with any and all other possible beings — existed, and existed necessarily. And, therefore, God existed.
WHAT I find impressive about this proof is the way in which it seeks to address atheists on their own terms. It starts with a premise that Prémontval knew that atheists accepted, and, as such, it reveals a degree of understanding of the atheist position which is typically lacking in other proofs.
Also, whereas other proofs try to force atheists into accepting that their position is wrong, Prémontval’s is subtler, in that it tries to show atheists that, if they consider their own principles properly, they will realise that they are, in fact, committed to the existence of God after all.
Prémontval’s subtler approach is almost certainly due to his having, when he was younger, been an atheist himself. At the age of 30, however, he converted to an unspecified branch of Protestantism. His proof was published almost ten years later. Although he never says this, it is possible that Prémontval’s proof captures the sort of reasoning that led him away from atheism when he was young. If it does, then this may be one of those rare cases in which a proof of God’s existence has successfully done what it was designed to do: win over an atheist.
GIVEN this, we may wonder whether today’s believers ought to make use of Prémontval’s proof when trying to win atheists round. My suspicion is that few believers would want to use it, on account of some of its more curious features.
Most notably, if the proof succeeds, then it proves the existence of everything possible. Also, it automatically rules out the doctrine of creation: by insisting that every possible being exists, and exists necessarily, it leaves no room for the creation of anything, by God or anyone else. Prémontval’s proof is, therefore, at odds with orthodox theological thinking, which holds that God created the universe and everything therein.
If the aim is to win round the atheist not just to a belief in the existence of a God but to a traditional, orthodox kind of theism, then Prémontval’s proof is not the right tool for the job. Although it speaks directly to atheists, it also takes them in a direction that most theists would not want them to go in.
Therefore, in spite of its ingenuity, Prémontval’s proof is not likely to find its way into the believer’s arsenal any time soon.
Dr Lloyd Strickland is Professor of Philosophy and Intellectual History at Manchester Metropolitan University. His book Proofs of God in Early Modern Europe is published by Baylor University Press.