Thursday, March 28, 2013

A presentist argument for the Principle of Sufficient Reason, well sort of

  1. (Premise) If presentism is true, reality is present reality.
  2. (Premise) All contingent facts about present reality have explanations in terms of how the world used to be.
  3. So, all contingent facts about present reality have explanations. (By (2))
  4. So, if presentism is true, all contingent facts have explanations. (By (1) and (3))
Premise (2) is the controversial one. But it might be accepted even by someone who thinks the world came into existence causelessly, since present reality would still have an explanation.

It is, of course, unclear that the presentist can deliver on (4), since it is not clear that the presentist really can explain things in terms of how the world used to be. That depends on how well the grounding and causality objections can be answered by the presentist.


Eric Reitan said...

Shouldn't (4) be "So, if presentism is true, all contingent facts have explanations"?

Alexander R Pruss said...


Alexander R Pruss said...

I fixed it. For those who come to this post later, the original version of (4) just said "So, all contingent facts have explanations."

Michael Gonzalez said...

Despite the fact that I strongly support both presentism and the PSR, and moreover I am a theist and have no problem with the world having a cause, still I wonder about premise 2 in your argument here. If one does not accept the PSR, then one could believe that a certain part of present reality has no explanation. All things that do have explanations, would have the kind that refer back to previous events. But that doesn't actually entail that everything that is true now has such an explanation (or any explanation at all).

Mike Almeida said...

PSR is a necessary truth, if true, no? It would be really weird if PSR held contingently. But if it is a necessary truth, (if true), then we might have a interesting argument for it based on presentism. You will need to add the fact that all possibilities are actualized somewhere, presently, given an infinite space-time. And all possibilities have an explanation.

Alexander R Pruss said...


There are times when Leibniz sure seems to be saying that PSR is only contingently true.

But I think it's necessarily true. Still, there are arguments for necessary propositions that only establish the actual truth of the proposition.


Yes, not every presentist PSR-denier will go along with the argument. But those who think that only the beginning of the universe lacks an explanation might be tempted to.