enough to give it. And, because it freely causes the existence of the universe, the act of
creation is a self-explaining action for a libertarian theory of freedom, which is the theory
favored by the theist.
Once our opponent realizes that W-PSR logically entails S-PSR, she might no longer
grant us W-PSR, charging it with begging the question. Whether an argument begs the
question is relative to the epistemic circumstances of its opponent before the argument is
given, not after it has been given. But this response would not silence Graham Oppy, for
he claims that “once you understand W-PSR properly, you can see that it entails S-PSR;
and S-PSR is something which nontheists have good reason to refuse to acceptThose
nontheists who were `willing to grant W-PSR' before they heard the argument which
Gale and Pruss give should then say that they didn't fully understand what it was to which
they were giving assent” (2000, 349). Herein Oppy is demanding that proper or full
understanding be closed under deduction. This demand is contrived and has the unwanted
consequence that every valid deductive argument, when its premises are fully understood,
can rightly be charged with begging the question.
Although Oppy's demand is unacceptably strong, it still is true that to have an adequate
understanding of a proposition one must know some of its entailment relationships. One
would not understand, for example, the proposition that this is a material object unless
one were prepared to deduce from it that this occupies space. (Please, no Castenada-type
counterexamples of the “I went to kiss Mary but her lips were not extended” sort!) But,
plainly, one can understand that this is a material object without being aware of the very
complex propositions that it entails within mereological theory.
We are not able to give a precise criterion for distinguishing between those entailment
relations that are constitutive of understanding a given proposition and those that are not,
since the concept of understanding is a pragmatic one and thus context-sensitive. But this
does not mean that we cannot identify clear-cut cases of someone understanding a
proposition and those in which she does not. And certainly one can understand a
proposition that uses a modal concept without knowing every theorem of modal logic,
just as one can understand a proposition employing geometrical concepts without
knowing every theorem of geometry.
The most challenging objection to our argument has been given by Kevin Davey and Rob
Clifton (2001). Their strategy is to find a proposition that is strongly incompatible with
W-PSR, in that if either is true in any possible world the other is true in none, and which
is at least as plausible a candidate for being logically possible as is W-PSR. Their
candidate for such a proposition is that there is a contingent proposition that lacks an
explanation in the actual world, say that
end p.126
there are cats, or the universe for that matter. This modal intuition seems at first blush to
have as much prima facie plausibility as does our modal intuition that every contingent
proposition possibly has an explanation. But it turns out that these plausible modal
intuitions are strongly incompatible. For W-PSR entails S-PSR and thus that in no
possible world is there an unexplained contingent proposition. But the Davey-Clifton
intuition entails that there is just such a world.