Monday, May 23, 2011

Modal Epistemology and Plantinga's Free Will Defense

A key claim in Plantinga’s free will defense is that:

(TWD) Possibly, every creaturely essence suffers from transworld depravity.

To elaborate a bit: Say that a world is feasible if and only if it’s a possible world that God can at least weakly actualize. Then TWD asserts that there is a possible world W such that, from W, there is no feasible world W’ at which libertarianly free creatures freely do right on every occasion.

For our purposes, it’s important to note that TWD crucially involves the metaphysical possibility of libertarian agency. But suppose that knowledge of what’s possible is grounded in basic and inferential knowledge of what’s actual, and that knowledge of the possibility of libertarian agency isn’t grounded in basic or inferential knowledge of what’s actual. If so, then we don’t know whether libertarian agency is possible. And if not, then since Plantinga’s free will defense requires the metaphysical possibility of libertarian agency, it follows that we don’t know whether TWD is possibly true, in which case Plantinga’s free will defense fails to justify the claim that God and evil are compatible.

But perhaps one will reply that all Plantinga needs for the success of the free will defense is the mere epistemic possibility of TWD. Here we must be careful, though. For there are at least two construals of the notion of epistemic possibility:

Weak Epistemic Possibility: P is weakly epistemically possible if and only if P is logically consistent with what we know.

Strong Epistemic Possibility: P is strongly epistemically possible if and only if there's a decent chance that P is is the case, given what we know.

But clearly Plantinga’s free will defense cannot undercut the logical problem of evil if TWD is merely weakly epistemically possible. For then TWD is on a par with the skeptical scenarios associated with radical skepticism about perceptual knowledge, such as the possibility that we’re brains in vats, or the possibility that we’re in the Matrix. But just as the mere weak epistemic possibility of such skeptical scenarios is insufficient to undercut the prima facie justification enjoyed by our perceptual knowledge, so the mere weak epistemic possibility of TWD is insufficient to undercut the prima facie justification enjoyed by the key premises of the logical problem of evil.

But what if we construe it as a strong epistemic possibility? Clearly, Plantinga's Free Will Defense would be a success if TWD were strongly epistemically possible. Unfortunately, though, only a limited audience will find TWD to be strongly epistemically possible for them. Thus, consider John. John is convinced by careful evaluation of the relevant arguments and evidence that some non-libertarian theory of agency is true or plausibly true. Because of this, TWD isn’t strongly epistemically possible for John, in which case Plantinga’s FWD fails to deflect the logical or deductive argument from evil for him. Now here’s the rub: unless you fall within a certain subset of theists, or a much smaller subset of non-theists, you’re probably like John in your views about the nature of human freedom.

The upshot, then, is that if our knowledge of what's metaphysically possible is grounded in our knowledge of what's actual, then Plantinga’s free will defense is of very little help in responding to the logical problem of evil.

6 comments:

TaiChi said...

"The upshot, then, is that of our knowledge of what's metaphysically possible is grounded in our knowledge of what's actual, then Plantinga’s free will defense is of very little help in responding to the logical problem of evil."

It's of little help if Plantinga seeks to persuade others that the logical problem of evil fails. On the other hand, if he does not seek to persuade others, but merely to defend his belief on grounds that he can accept as plausible, then your argument does not show that he fails in this. And I think there's plenty of evidence that the latter is Plantinga's goal: Warranted Chrisitan Belief is an exercise in this, a work of apologetics.

That said, I tend to think that he fails even in this lesser goal. Have you read, for example, Raymond Bradley's essay on SecWeb?

http://www.infidels.org/library/modern/raymond_bradley/fwd-refuted.html

exapologist said...

Hi TaiChi,

Thanks for the reference! I look forward to reading it.

I see what you're getting at re: Plantinga's aims wrt his version of the free will defense, and I've tried to highlight this as well on another occasion. However, if I'm right that all our knowledge of what's metaphysically possible is ultimately grounded in our basic and inferential knowledge of what's actual, and a crucial modal claim in Plantinga's FWD isn't grounded in our basic or inferential knowledge of what's actual, then wouldn't that undercut even Plantinga's weaker claim that he's warranted or justified in accepting the FWD?

TaiChi said...

"I see what you're getting at re: Plantinga's aims wrt his version of the free will defense, and I've tried to highlight this as well on another occasion."

Yep, I've read that post. I left a belated comment there, perhaps you missed it?

"However, if I'm right that all our knowledge of what's metaphysically possible is ultimately grounded in our basic and inferential knowledge of what's actual, and a crucial modal claim in Plantinga's FWD isn't grounded in our basic or inferential knowledge of what's actual, then wouldn't that undercut even Plantinga's weaker claim that he's warranted or justified in accepting the FWD?"

From whose point of view? Since you and I believe that our actual knowledge does not make TWD a significant possibility, then from our point of view, Plantinga's claim is undercut (and we can reject the theist's claim that the logical problem of evil has been solved). But many theists take the truth of libertarianism to be part their actual knowledge, and so take TWD to be a significant possibility: for these people, Plantinga's claim is not undercut. Since it's not clear to me that your post offers anything to persuade the latter that TWD is not metaphysically possible, I can't see that it progresses the debate. Or am I misreading you?

exapologist said...

Good thoughts. I suppose Plantinga could argue that his belief in libertarian agency is properly basic (but then I think he's stretching it: if the overwhelming majority of Christians in even his own denomination reject libertarianism as properly basic, then the case for proper basicality is looking pretty flimsy, methinks). However, even Plantinga admits that he has to deal with potential defeaters, and that would require, at a minimum, offering defeaters for all the non-libertarian theories. To date, though, I don't think he's done any such thing. So at a minimum, I think my view, if correct, would require him to do more work than he's actually done.

James said...

Isn't the logical problem whether the conjunction of a good/powerful/wise God with the existence of evil is necessarily false? The answer turns not on the relative likelihoods but on the existence of a logically consistent model containing the conjunction. Or am I missing something?

exapologist said...

Hi, James.

As Plantinga has noted, mere logical consistency is cheap, as many logical possibilities are yet metaphysically impossible. Plantinga needs a defense of the logical problem of evil that's (what he calls) "broadly logically possible", i.e., metaphysically possible. Other philosophers have pointed out, though, that in some dialectical contexts, Plantinga only needs something weaker: epistemic possibility. And my point is that if justification of epistemic and metaphysical possibilities are grounded in our knowledge of what's actual, then Plantinga's FWD is of little help in responding to the problem of evil.

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