Saturday, May 3, 2008

Philosophy needs the Principle of Sufficient Reason

I claim that much of philosophy depends on the Principle of Sufficient Reason (PSR), namely the claim that all facts have explanations.

It is morally acceptable to redirect a speeding trolley from a track on which there are five people onto a track with only one person. On the other hand, it is not right to shoot one innocent person to save five. What is the morally relevant difference between the two cases? If we denied the PSR, then we could simply say: “Who cares? Both of these moral facts are just brute facts, with no explanation.” Why, indeed, suppose that there should be some explanation of the difference in moral evaluation if we accept the denial of the PSR, and hence accept that there can be facts with no explanation at all?

Almost all moral theorists accept the supervenience of the moral on the non-moral. But without the PSR, would we really have reason to accept that? We could simply suppose brute contingent facts. In this world, torture is wrong. In that world, exactly alike in every other respect, torture is a duty. Why? No reason, just contingent brute fact.

The denial of the PSR, thus, would bring much philosophical argumentation to a standstill.

Note: This, like the previous post and at least one earlier post, is an excerpt from a paper I am finishing on Leibnizian cosmological arguments.


Anonymous said...

Does this really make the PSR necessary? Why not say that there's a rational norm that we seek explanations when there is no good reason to suppose that one cannot be found--which falls short of saying that every fact does have an explanation? True facts for which there is not an explanation and reason to suppose that there is no explanation could include the existence of God and Jones's libertarian-free choice for option X over its available alternatives.

Alexander R Pruss said...

Would the fact that an explanation has not yet been found, despite lots of searching, count as a good reason to suppose that one cannot be found?

Anonymous said...

Yes. Good but not decisive.

Alexander R Pruss said...

The problem is that then this could easily lead to defeatism...

Anonymous said...

Defeatism, meaning what exactly? That I just stop looking for explanations and give up as soon as things get difficult? I doubt that giving up PSR would do that, because even if PSR is not true, there are still explanations for a very wide range of facts, and the presumption that any given fact has an explanation should be strong enough to sustain continued attempts to figure out what it is. Giving up PSR wouldn't lead to defeatism (of course it might, but that would be a psychological matter, and the difficulty of saying anything at all coherent when doing metaphysics seems to lead more people to metaphysical defeatism than giving up PSR has; but you can't eliminate that difficulty, and you can see that it provides no good reason for defeatism). Rather, giving up PSR would keep us from insisting that we either have some explanation for a fact when our putative explanation is really insufficient or that, in the absence of an explanation, the alleged fact just isn't a fact -- which is just what determinists do with libertarian-free choice.

Alexander R Pruss said...

Why, though, without the PSR would there even be a presumption that there is an explanation? What would ground the presumption?

Is it that it is probable that a proposition has an explanation? But what would that probability be grounded in?

Wesley C. said...

Have you read Terence Cuneo's The Normative Web ?

In that book, he talks about how moral realism can be stablished from parallels in epistemology and epistemic obligations people commonsensically assume they have.

What is most important is his discussion in that book on why epistemic nihilism (which is parallel to moral nihilism) ends up saying that there are no epistemic obligations. No proposition is such that it is actually belief-worthy, and no entity can display epistemic merit or demerit because there are no epistemic reasons.

It also implies that no arguments are valid, because premises don't offer any evidential support whatsoever of themselves.

I don't know if this could actually be done, but what I'm most interested in is if an argument for PSR could be made by proving how PSR-denial would inevitably lead into epistemic nihilism, if not ontologically (there really are no epistemic facts, obligations and merits because all of our thoughts and reasons we have for holding epistemic realism could be brute facts) then at least epistemologically (our rational thoughts and deductions, though they seem to us as being necessary conclusions that follow from logical syllogistic form, could all be brute facts and not really follow true epistemic standards).

If we could prove that rejecting the PSR opens up the possibility of ontological epistemic nihilism (as Cuneo describes it in his book), then we could make a retorsion argument that goes much deeper than mere radical skepticism. A rejection of PSR could put in jeopardy epistemic realism itself and threaten with a wholesale epistemic collapse if we don't believe that PSR actually holds.

What do you think?