Against Parthood∗ - Ted Sider

according to Pryor, continue to justifiably believe in what I perceive (hence
his name for his position: dogmatism). Might it be argued that the nihilistic
hypothesis is a skeptical challenge to perceptual beliefs in composites, not an
ordinary challenge, and hence that perceptual justification in composites does
not vanish in the way that I have been arguing? There’s no reason to think that
Pryor intended the notion of a skeptical challenge to be understood in this way;
but might this position be defended?
The nihilist’s challenge differs from the skeptical one in that, intuitively, it is
a real contender to be believed, whereas the brain in a vat hypothesis is a mere
possibility—something that is hard to independently rule out but for which we
have no positive evidence. It is hard to make this distinction precise, but the
following factors seem relevant. 1. By ordinary standards, nihilism is supported
reasonably well by the evidence (so long as that evidence is construed neutrally;
but see the discussion of Williamson below), whereas the vat hypothesis is not.
2. Nihilism gives a satisfying explanation—again, by ordinary standards—of
our perceptual experiences; the vat hypothesis does not. 3. There are positive
reasons to believe nihilism, but not the vat hypothesis. 45
Are these differences enough to rebut the idea that the nihilist’s challenge
is a skeptical one? The notion of a “skeptical challenge” is not a precise one, so
it is hard to say anything definitive here. But perhaps the following bird’s-eye
remarks constitute progress. There is a point to having a concept of justification
that allows skeptical challenges to be summarily dismissed: namely, to
avoid the stultification of inquiry. If explanation-givers needed to be able to
answer the challenge posed by each and every alternate explanation, including
the brain-in-the-vat “explanation”, then we would never get anywhere. But a
concept allowing nihilism to be dismissed in this way would also be stultifying.
It would encourage tunnel-vision, limiting our attention to the familiar, and
discouraging the consideration of radically new approaches to old problems.
(Indeed, openness to unfamiliar viewpoints is part of what philosophy is most
concerned to teach.) I don’t think our existing concept of justification is stultifying
in this way, so I don’t think the nihilistic challenge can be dismissed in
the way that the skeptical challenge can. But if this is wrong as a descriptive
matter, then so much the worse for our existing concept of justification. We
ought then to adopt a better concept that is more tolerant of challenges to the
45 Compare Pryor: “I don’t want to claim that you never have to rule out skeptical hypotheses…
[Prima facie justification for perceptual beliefs] can be undermined or threatened if you
gain positive empirical evidence that you really are in a skeptical scenario.” (2000, pp. 537–8, my
emphasis).
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