Thursday, November 8, 2012

A simple argument that the PSR is necessarily true or necessarily false

Aron Zavaro, in correspondence, supplied me with the following simple central idea for this argument: If the Principle of Sufficient Reason (PSR) were contingently true, there would be no explanation of why it is true.

So the PSR is either necessarily true or necessarily false.

20 comments:

Drew said...

How do you define the PSR, and how do you reconcile it with libertarian free will?

Alexander R Pruss said...

See either my PSR book or this.

Heath White said...

This is a neat little argument.

It works, I think, iff explanations must entail their explananda. For suppose they don't have to entail their explananda. Then the PSR can be contingent so long as I can give an explanation of the PSR which does not entail it.

Alexander R Pruss said...

It depends. While some things do have non-entailing explanations--say, outcomes of stochastic processes--it is hard to see a very plausible story on which the PSR has such an explanation.

Houdini said...

Dr. Pruss, I have a question concerning Koon's epistemological argument--I believe you presented a shortened version in your Leibnizian Cosmological Argument. It seems as if Koons is arguing that if ~PSR is true then it's possible that our perceptual states are brute facts (either part of the time or all of the time). Therefore, we could have no trust in our perceptual sates. But, of course, even if ~PSR is true it still might be the case that our perceptual states aren't brute facts and that perhaps other things in the external world are. In fact it might be the case that only one thing is a brute fact, or three, or three-hundred. But ~PSR doesn't necessarily entail that our perceptual states are brute facts. But this means that Koons is arguing from mere possibility. That is, if it's even possible for ~PSR to be violated--and to be violated with regards to our perceptual states--then we can have no trust in the veracity of our perceptual states.

If Koons is basing his argument off of mere possibility (i.e. that PSR isn't necessarily true and can possibly be violated) then, even if ~PSR were false and PSR true we would still fall into radical skepticism concerning our perceptual states. It's logically possible, even if PSR is true, that we are brains in vats or being controlled by some higher power (Descarte's demon for example). And since it's possible that these scenarios are true then, like Koons' argument, we can't trust our perceptual--heck!--even our cognitive states. So it seems to me that Koons' argument is actually too broad. If we're going to argue from mere possibility that ~PSR entails radical skepticism concerning our perceptual states, then we should equally affirm radical skepticism with regards to demon or brain in vat scenarios (seeing how they are possible scenarios).

Houdini said...

Well not so much a question as it is a criticism. I'm wondering if you can answer it.

Alexander R Pruss said...

My preferred move is that if PSR is false, then one cannot say that such sceptical scenarios are *unlikely*, because no meaningful probabilities can be attached to violations of PSR.

Houdini said...

I'm not even sure we can determine the probability of these sceptical scenarios even with PSR. For suppose we take the evil demon route. Any attempt to prove that such a scenario is unlikely would presuppose that our cognitive faculties are reliable and can subsequently draw a conclusion from certain evidences. But if such a demon existed then we couldn't trust our cognitive faculties at all.

Alexander R Pruss said...

We might have a deductive argument for the existence of God, and then argue that God isn't likely to allow much in the way of such demonic deception.

But more generally, I think that if our metaphysics commits us to the non-unlikeliness of a sceptical scenario, then either we should doubt that metaphysics or we should be sceptics.

Houdini said...

Yes but using a deductive argument against an epistemic scenario like the demon would be to presuppose that one isn't already in the grasps of the demon and can consequently rely on their cognitive faculties to make a sound deductive argument. How can one tack any degree of probability to a sceptical scenario without presupposing that the sceptical scenario is false?

Philarete said...
This comment has been removed by the author.
Philarete said...

Forgive me if my questions are naive, but here I go :

- Why are we assuming here that if the PSR were contingently true, it would have no explanation ? After all, many propositions are contingently true (e.g., I skipped breakfast today) but do admit an explanation. Thus, why would it be a problem to say that the PSR is only contingently true but with an explanation ?

-Secondly, couldn't we say that there are such things as contingent explanations ? Assume the PSR is true. Then, there must be an explanation why it is true. What would preclude the possibility of there being a contingent explanation of this fact?

Alexander R Pruss said...

Sure, but it's really hard to think what a contingent explanation of the truth of the PSR would be like.

Manuel said...

How do you reconcile the PSR and Brute facts?

Unknown said...

What's your opinion on the objection that quantum fluctuations and virtual particles break PSR?

Alexander R Pruss said...

Manuel:

There are no brute facts if the PSR is true.

Unknown:

There are indeterministic causal explanations. If we have a quantum state a|A>+b|B>, then the state has a causal power of collapsing into A, and a causal power of collapsing into B. If it collapses into A, that collapse is explained by its power of collapsing into A and the fact of observation, and ditto with B in place of A.

Joe. said...

Dr. Pruss, causal powers explaining causal powers is a vicious regress. which is why you have a set of relations i.e. power-manifestations. The only way you can detour around that is if you hold non-powers and deny pandispositionalism and categoricalism in favour of a janus-faced dispositionalism. Which not many do

Joe. said...

Like, without defining what the manifestations ought to be in the quantum state then you have causal powers explaining causal powers which is a vicious regress. (and without the manifestations in grounded in place then you also have trouble with getting the density matrix even without real numbers and instead expressions) just accept a framework where categorical properties individuate causal powers or any sort of dispositional property i.e, not every dispositional property is inherently causally significant and yields causal complexity (travis dumsday says this in Dispositionalism and the Metaphysics of Science)

it's even more stupid to describe a quantum state having any sort of causal powers; the sakurai conceptualization of stern-gerlach experiments (where there is ionization of energy in iron and it splits in two in a two dimensional vector space e.g., up or down) literally just shows the bringing about something not necessarily arbitrary but rather they just somehow split into two; it isn't a causal power being actualized by some one stimulus condition to split the two—it isn't a grounded dispositional property with any sort of metaphysical determination to bring about something

Joe. said...

Dr. Pruss what’s your thoughts regarding my comments.

Joe. said...

Also there's still probability distribution. |¤łA⟩=1/2√(|↑⏐⟩+|⏐↓⟩) . since you add two wave functions together you get a new one so we get mix b; BUT NO, it's a two dimensional vector space in a inhomoegenous state, so no you will not get a new wave function.

actually what you said was pretty much the probability distribution of the stern gerlach thing