Let Contingentism be the thesis that no concrete thing must exist. Define ‘concrete thing’ as anything that can cause something, or leave it as primitive. (Side note: Contingentism is hotly debated among philosophers of religion. But surely it is a thesis of metaphysics; so why aren’t metaphysicians debating this?)
Arguments against Contingentism typically take the following form:
1. Every fact of type T has an explanation (else: is explicable)
2. If Contingentism is true, then there is a fact of type T that has no explanation (else: is not explicable)
3. Contingentism is not true.
Committed Contingentists usually either end up denying the principle of explanation employed by (1) or withholding judgment. After all, such explanatory principles tend to be very far-reaching.
But here’s another strategy. We count costs. Rather than searching for sound philosophical arguments for/against Contignentism, we identify costs and benefits of Contingentism. That may be a lot easier. And it can help us make progress without having to make converts: for a committed contingentist can, in principle, come to agree that there are certain costs of Contingentism.
I’m going to propose one cost–to get this strategy started. (I do not claim this is the most serious cost, or that there aren’t counter-costs that ultimately outweigh it.)
The cost is that there is a fact that cannot have an explanation if Contingentism is true but can have an explanation if Contingentism is not true. Hence, Contingentism implies a mystery that its denial would resolve. And that’s a cost–be it big or small.
Which fact? I think there are many, actually. Here’s one: the fact C that the c’s exist at all, where ‘the c’s’ plurally (and rigidly) refers to all contingent concrete things. Unless we allow circular explanations, it seems that an explanation of C would be at least in part in terms of something other than one of more of the c’s (no matter how many c’s there are). But Contingentism does not allow for the existence of anything other than the c’s. Thus, Contingentism doesn’t seem to allow C to have an explanation.
On the other hand, if Contingentism is false, then we could suppose that C is explained by a causal chain that is headed by one or more concrete things whose existence is explained by the fact that it/they must exist (for instance).
Now someone might quibble with my example. (There’s the classic objection that the fact that the c’s exist could somehow be explained by the fact that each is explained by another, ad infinitum… (but would that explain why those c’s exist at all?) … I’ve also encountered the idea that contingent things could be explained in some sense by their having a nature that makes them indestructible and beginningless…) But then shift to a different example: let E be the fact that being a contingent concrete thing is exemplified. It seems that no facts about contingent concrete thing(s) could explain E without circularity, and surely E isn’t explained by virtue of being necessary (for surely there could be no contingent concrete things: think principle of recombination).
Here are a some additional candidate examples: (i) the fact that the c’s have the total space-time geometry they do; (ii) the fact that there are n contingent things, where ‘n’ names the number of contingent things there are; (and for fun (iii) the fact that the c’s possibly exist [if Alex is right that a thing possibly exists only if there’s something has the capacity to head a causal chain that leads to its existence]).
One can of course suppose that none of these facts have an explanation. But since we can explain those facts (in straightforward, non-gerrimandered ways) if Contingentism is false, it seems there’s a cost to holding Contingentism.
Of course, admitting necessary concreta could be even more costly. I have only argued that Contingentism has a certain cost, and perhaps even committed contingentists can agree.