Williams aims at a theoretical diagnosis of the sceptical argument. He claims that the sceptical argument depends on what seemed merely an accidental feature of Descartes’ method of doubt: treating our knowledge of the external world as a single type of knowledge, sharing a common style of justification (via (our knowledge of) our experience). But the idea that there is such a class as ‘our knowledge of the external world’ is not a natural idea and this category is theoretical and artificial. So once we realise that the sceptic relies on this assumption – for example in the way normal ways of justifying our claim that we are not now dreaming are ruled out because we need to prove we are not dreaming independently of anything else we know about the world – it is equally possible to reject both it and the scepticism it leads to. Further, the very fact it leads to scepticism (which is obvious rubbish) counts against it.
Williams also provides some further comments to try to persuade us that as ‘our knowledge of the external world’ is not a natural idea. His comment that Descartes’ claim that our bodies are external seems spot on.
Is this enough to stop scepticism? Unlike Putnam, he does not claim that the sceptical hypothesis makes no sense. So he does not say that scepticism makes no sense. That may count in his favour (since scepticism seems to make sense). But, unlike Davidson, he does not let the sceptical argument go through. Once it does it seems merely dogmatic to attempt to deny it. Instead, Williams aims to show that scepticism depends on a theoretical view of knowledge which is neither obligatory nor natural.
Still, one might think that the sceptical possibility is the most natural aspect, not of everyday life but certainly, of philosophical inquiry. That is, as soon as one begins to think about knowledge, one realises that there is a central tension in what we take it to be and in our taking ourselves to have it. So in the end, Williams may trade intuitions about what is and is not natural.
If that is how things stack up then one way one might aim to break the deadlock is by considering the plausibility of what Williams opposes to epistemological realism (the view that our knowledge of the external world as a single type of knowledge sharing a common style of justification). What is the alternative? Contextualism.
Epistemological realism takes it that good justifications have a common feature: they start with our experience construed as not presupposing any knowledge of the external world and then work outwards to the external world. What does contextualism take all good justifications to have in common? Nothing (well, nothing substantial). Justification depends on, and varies with, context.
It would be good to learn more of what this involves (see Wittgenstein later). But if contextualism is a better account than epistemological realism (before we consider scepticism) then since scepticism needs a prior assumption of realism, that really would count against scepticism.
"But hang on. If there are two views of knowledge and justification in play: epistemological realism and contextualism (where the former leads to scepticism), then isn't the idea that this blocks scepticism merely dogmatism at one level up. At the ground level, sceptical hypotheses or ringers don't have to be true, they just have to be possible. Their mere undetectable possibility is enough to undermine knowledge - because even if our beliefs about the external world are true that is mere luck in the face of the ringers - and thus lead to scepticism. So equally at this higher level of abstraction (concerning knowledge of the nature of knowledge rather than trees etc), epistemological realism doesn't have to be true, it just has to be possible, for that fact to undermine, via the standard sceptical argument, ground level knowledge and thus lead to scepticism."
I don't think so. After the sceptical argument is already up and running, then the fact that we have a stand-off between epistemological realism and contextualism might be enough to hand the victory to scepticism. (First, if we have already granted that we don't know that that! is a tree, then we will not likely know the nature of knowledge either and then, second, if we do not know that contextualism is true then we won't know that that! is a tree: a kind of mutually supportive sceptical collapse.) But Williams contests the argument before the sceptical argument is complete for the first time.
So the stand off between epistemological realism and contextualism is more neutral. It is played out on ordinary pre-sceptical grounds. Only if we have reason to think that epistemological realism is reasonable can the way the sceptic sets up his ringers be reasonable and thus, for the first time, make us concede that we don't have knowledge. But if our response to the sceptic's initial claim - that our knowledge of the world depends on a more certain knowledge of experience - was that that was an absurd idea (because, eg. I only learn to talk about my experiences long after I learn to talk about trees etc), then we would never have been worried about scepticism in the first place. Nothing would follow from the mere existence of sceptical ringers.