Thursday, October 7, 2021

Could the PSR be contingent?

The Principle of Sufficient Reason (PSR) says that every contingent truth has an explanation. Most people who accept the PSR think it is a necessary principle. And there is good reason, because it seems more like a candidate for a fundamental necessary truth than a merely contingent fact. And epistemically, if the PSR is contingent, it is hard to see why we should think ourselves lucky enough for it to be true.

All that said, it is interesting to investigate the question a bit more. So, let’s suppose the PSR is contingently true. Then according to the PSR, the PSR has an explanation, like every other contingent truth. What could the explanation of the PSR be like?

Since we’ve assumed the PSR to be contingent, the explanation can’t simply involve derivation of the PSR from necessary metaphysical principle.

The explain a contingent PSR is to explain why no contingent unexplained thing has happened.

Here is one suggestion. Perhaps there is a necessary being which has the power to prevent the existence of contingent unexplained events. This necessary being freely, but with good reason that the necessary being necessarily has, chooses to exercise this power. Thus, the explanation of why no contingent unexplained thing has happened is that the necessary being freely chose to prevent all such things. And the necessary being’s free choice is explained by reasons.

I am not sure what I think of the plausibility of a hypothesis of a being as having the power to prevent things from popping into existence causelessly if such popping is otherwise metaphysically possible.

Here is another much less metaphysically loaded attempt. It seems to me that whether one accepts the PSR or not, one should accept instances of the following kind of explanatory schema for contingent events E:

  1. Event E did not happen because there is no explanation of E.

If the PSR is necessarily true, then the fact that there is no explanation of E entails that E did not happen. However, I think we should accept instances of (1) even if the PSR is contingently true and even if it is not true at all. In those cases, that there is no explanation of E may not entail that E did not happen, but we shouldn’t think that explanations must entail the events they explain. (If we thought that, we would have to reject most scientific explanations.)

Now imagine we have an infinite list of all possible contingent events that could happen but did not happen, E1, E2, ..., and an infinite list of all contingent events that did happen, F1, F2, .... We can then say:

  1. The PSR is true because E1 did not happen, E2 did not happen, E3 did not happen, while on the other hand F1, F2, ... did happen.

And why did Ei not happen?

  1. Ei did not happen because there is no explanation of Ei.

And of course each of the Fi does have an explanation, because the PSR is, we have assumed, true.

This seems like an explanation of the contingent truth of the PSR.

Both options seem a bit fishy, though. I can’t say exactly what’s wrong with them, though.


Wesley C. said...

I like your point about how it seems weird to say that an omnipotent necessary being can prevent a causeless explanationless event from happening. In fact, if God did exist and brute happenings were possible, it seems likely they would compete, or even cancel each other out.

Say a necessary being omnipotently sustains the universe in existence - what's there to prevent it from popping out of existence for no reason? If NB somehow vetos this, how does NB do that?

It seems that if you deny causality for something, that thing would be immune to any causal attempt to stop it, since it's not bound by causality, therefore it seems likely that it can't be affected by causality either. It could just be incoherent to talk of Brute stuff being prevented or cancelled out by something with causality.

Interestingly enough, it seems Brute Happenings would be omnipotent since any possibility that could be real also could be realised for no reason. Of course, BH isn't an actual cause, so we can't ascribe power to it in any sense as power is a causal term.

But nonetheless, it seems as if Brute Happenings is what you have if you take omnipotence and make it hang in the air with nothing to ground it.

Wesley C. said...

I also wonder if one could make a conceptual argument against the metaphysical possibility of Brute Facts by analysing what it means for a potency to become actualised - the very language of becoming seems to already presuppose causality subtly, so to talk of a potency becoming actual with no cause or explanation seems incoherent on that ground.

The very ontological shift from potency to actuality seems to have causality built into its metaphysics - that's just what it means to shift. Now this is just a crude intuition on my part, but I wonder if we can expand it a bit.

What do you think?

Walter Van den Acker said...


I think the PSR is either necessary or impossible, because if in w1 every contingent thing has an explanation, then we either get an infinite regress of contingent things explaining each other, or a necessary being explaining the contingencies.
But if contingencies are explained by a necessary being, we are stuck with a necessary PSR.
The only way for the PSR to not apply in a possible world is if it is possible for some contingent thing not to have an explanation at all.
But if something is possible, it is necessarily possible.

Alexander R Pruss said...


"But if contingencies are explained by a necessary being, we are stuck with a necessary PSR."

This is plausible, but needs more argument. What if what happens is this: the necessary being choose to explain all contingencies but could instead have chosen to allow unexplained contingencies to happen ?

Walter Van den Acker said...


An unexplained contingency has nothing to do with a necessary being. In fact, if there are unexplained contingencies (or brute facts) it is hard to see why a world with only contingent beings would be impossible. But that would mean there can be no necessary beings.

Unknown said...


Doesn't that argument assume that causation entails the effect? If one denies this, then one can say that a necessary being causes contingently.

Alexander R Pruss said...

I don't see where that assumption is made or which argument is affected by the supposition that a necessary being causes contingently (which indeed is what I think).

RunDec said...

"In fact, if there are unexplained contingencies (or brute facts) it is hard to see why a world with only contingent beings would be impossible."

That just doesn't follow. If unexplained contingencies are possible, this doesn't make a necessary being impossible. The existence of an unexplained contingency in one possible world doesn't entail there are no necessary beings in any possible worlds.

Walter Van den Acker said...

I simply sad it is hard to see why a world (w1)with only contingent beings would be impossible.
I don't claim w1 is possible but if it is possible, there are no necessary beings (N)because in w1, N does not exist.

RunDec said...

That is true that if there is a world with only contingent things, then there is no NB. But if that world were possible, it couldn't be derived from the possibility of brute contingencies.

Brute contingency only entails that there is at least one PW in which there's some contingent things with no explanation. That's all. More would be required to motivate the different idea of a possible world consisting of nothing *but* contingent things (subtraction arguments, perhaps)

James Reilly said...

If the PSR is possibly contingent, then given the universality of causation, doesn't that mean it MUST be contingent ("whatever could be caused must actually be caused," as Christopher Weaver put it)? And if the PSR is contingent, and thus likely to be false in most possible worlds, doesn't that lead us to skepticism (as you noted with Rob Koons, our empirical knowledge requires the PSR to hold in most nearby possible worlds)?

It seems like the PSR needs to be a necessary truth in order to play the epistemic role that we want it to play.

James Reilly said...

Of course, I suppose if one regards the universality of causation as merely a restatement of the PSR, then it makes little difference overall (though I could simply be misinterpreting all of this).

Walter Van den Acker said...


I agree that more would be required, but I don't think it's an entirely different idea.
I mean, if contingent things with no explanation are possible, then what basis is there to claim that a world with only contingent things with no explanation is impossible?
I don't see that basis at all.