Person A declares: “Question everything!” Person B responds: “Why?”
What’s wrong with this flippant response? Perhaps nothing. William Lane Craig in his ‘Defender’s class’, when talking about the Moral argument, also provided an argument not only against moral scepticism, but scepticism in general. His argument went approximately as follows: the sceptic is committed to the claim that “one cannot know P without knowing that one knows P”. His response was then to ask how the sceptic knows that! – How does the sceptic know that knowing that one knows P is a constraint on knowing P? This response is intended to do away with the force of scepticism of course, but I think it may be more insightful than Craig realizes. How might the sceptic respond to such a dismissal of her scepticism? Well, she might well respond by saying that she has a rational intuition that in order to have knowledge one needs deductive closure. However, that entails that, even for the sceptic, rational intuition is foundational, and represents a starting point or a basic assumption. However, if the sceptic really believes that rational intuition is properly basic, then the sceptic is really just a very conservative rationalist – moreover, she has no justification for her conservatism. She ought perhaps to adopt the view that rational intuitions, like the Principle of Sufficient Reason, are properly basic, and that we are rationally justified in believing in any belief which presents itself with the apparent force of rational intuition in the absence of any defeater. If the sceptic accepts as a constraint on what can be known that one must begin by axiomatically assuming the deliverances of rational intuition, then it seems she has no reason for being unduly sceptical of other rational intuitions which she must reject in order to avoid being dragged up a Cartesian ladder to Theism.
In any case, it seems to me this might contribute to the project of building up a rational epistemology which axiomatically accepts a modal constraint on knowledge, and operates from there. I’ve proposed this before, and I tend to think that not only can almost nothing do better than this (bracketing, for the moment, the implication of Medieval epistemologies which involved the category of wisdom), but that certainly this does better than alternatives on offer in today’s academic market, such as any radical form of Empiricism.