Williamson on Judgment Skepticism

In chapter 7, Williamson discusses a type of skepticism he calls judgment skepticism. As he explains it, judgment skepticism "does not target the distinctive features of perception, memory, testimony, or inference" but instead "targets our practices of applying concepts in judgment" (p. 220). Williamson's paradigm example of a judgment skeptic is the person who, with van Inwagen, denies that mountains exist. Since it is the view of these folks that our ordinary geographical judgments are systematically false when understood strictly and literally, they count as judgment skeptics. Williamson then goes on to argue that judgment skepticism is on a par in important ways with skepticism about the external world.

There is some interesting stuff in this chapter about philosophical methodology, but I'm not quite sure what to say about that. So instead I'll raise two issues with the way he construes judgment skeptics like those who deny the existence of inanimate macroscopic objects.

First, he seems to think that judgment skepticism is going to have drastic consequences for the natural sciences. He says:

Judgment skeptical arguments apply to standard perceptual judgments, on which the natural sciences systematically depend: microscopes, telescopes, and other scientific instruments enhance ordinary perception but do not replace it, for we need ordinary perecption to use the instruments. If the contents of those perceptual judgments concern ordinary macroscopic objects, they are vulnerable to judgment skepticism about common sense ontology. If so, the empirical evidence for scientific theories is threatened. To assume that the evidence can be reformulated without relevant loss in ontologically neutral terms, in the absence of any actual such reformulation, would be optimistic to the point of naivety.

Well, perhaps I'm just being naive here, but I feel much more optimistic for such a reformulation project. At least, I don't see any reason to think that it couldn't be successfully carried out. Exactly what drastic consequence would follow for natural science if we agreed with van Inwagen that, strictly speaking, there are no mountains, or even that there are no telescopes? I just don't see it.

Also, he talks about judgment skeptics as though they argue for their position in a way precisely analogous to the more familiar sort of skepticism, but that doesn't seem true to me. As he points out, the skeptic about the external world may well argue employing the following bit of reasoning: since everything would appear to us exactly as it currently appears to us even if we were just brains in a vat, we don't know that we're not. The parallel move in the case of the van Inwagen-style skeptic would be: since it would still appear to us that there were mountains even if there were no mountains, we don't know that there are mountains. Perhaps someone who argued for mountain-skepticism using this sort of reasoning would be open to Williamson's objections, but van Inwagen doesn't argue in this way, does he? I thought the argument was supposed to employ more general mereological considerations about, for example, the downsides of DAUP and Unrestricted Composition, among other things. So it's unclear to me that judgment skepticism really is the sort of view Williamson is painting it to be -- or perhaps eliminativist views like van Inwagen's shouldn't count as versions of judgment skepticism after all?