Philosophical Issues 14 (2004)
Moore looked at his hands and argued:
(1) Here are two hands.
(2) If hands exist, then there is an external world.
(3) So there is an external world.
１．the proof Moore rehearsed is perfectly respectable.
２．（sections 3–4） the justificatory structure Moore was endorsing is a genuine one. Perceptual justification to believe you have hands doesn’t require antecedent justification to believe there’s an external
world; and it can make the latter hypothesis more credible for you.
* It was already agreed that if you have evidence that you’re in a
skeptical scenario, it will (to some degree) undermine your perceptual
justification to believe Moore’s premise (1).
* If you believe or suspect without evidence that you’re in a skeptical
scenario, that won’t undermine your justification for Moore’s premise
(1). But it will (to some extent) rationally obstruct you from believing
that premise on the basis of your experiences. So you won’t be able to
use Moore’s argument to rationally overcome your suspicions.
* In the happy case where you neither have nor have reason to have the
kinds of doubts the skeptic wants to induce, then the justification
your experiences give you for Moore’s premise (1) will be undefeated
and unobstructed. Having that justification for the premise will make
Moore’s conclusion more credible for you; and that justificatory
relationship is one that you can rationally endorse in your reasoning.
If Moore’s psychological and epistemic situation was the last one, then I
claim the reasoning he engaged in was perfectly legitimate.
Moore’s argument is directed at a skeptic. We’ve focused on the skeptic
who doubts whether our perceptual experiences give us any justification at all for our perceptual beliefs. Clearly Moore’s argument is not very dialectically effective against that skeptic. But it should be clear by now why that’s so. The skeptic has doubts that prevent Moore’s argument from rationally persuading him. There’s nothing wrong with the justificatory structure the argument articulates, or with Moore’s own reasoning. What’s wrong is that the skeptic has doubts he ought not to have.We just discussed how dialectically effective Moore’s argument will be against a skeptic.
Moore had a variety of anti-skeptical ideas, including his claim that we’re reasonably more confident that we have hands than we are of the premises in the skeptic’s arguments.But let’s just consider Moore’s argument from (1) and (2) to (3). Our question is: how satisfying a philosophical response to skepticism does that argument constitute?
＊Nowadays, it’s commonly agreed that an adequate philosophical
response to the skeptic need not be capable of rationally persuading the
skeptic that the external world exists, or that we have justification to believe it exists. Nor need it be capable of persuading someone who’s seized by skeptical doubts. What it does have to do is diagnose and explain the flaws in the skeptic’s reasoning. It has to explain away the intuitions that the skeptic draws support from. These are not responsibilities that one has as an ordinary believer. The ordinary believer who’s never heard the skeptic’s arguments—or who’s heard them but rationally believes they’ve got to be flawed somehow—doesn’t need to to do anything more, before he can believe with justification that the world is the way it looks to him. But they are responsibilities we have when we’re doing philosophy. That’s the business of philosophy: to diagnose and criticize arguments like the skeptic’s.
Clearly Moore’s argument, by itself, does little to discharge those
responsibilities. I think it does offer us a piece of reasoning by which we
can acquire justification to believe the external world exists. But it takes a lot of supporting argument—only some of which I’ve given here—to establish that. If we’re to have a satisfying philosophical response to skepticism, it will consist in that supporting argument, not in the reasoning that Moore’s argument articulates.