This morning, Jason Stanley (Rutgers University) delivered a paper entitled 'Knowledge and Action' at the Faculty of Philosophy of the University of Buenos Aires. Therein he defends the the following principles:
The Action-Knowledge Principle: Treat the proposition that p as a reason for acting only if you know that p.
The Reason-Knowledge Principle: Where one's choice is p-dependent, it is appropiate to treat the proposition that p as a reason for acting iff you know that p.
He formulates both principles by reflecting on what people actually say in ordinary life. One of the examples he gives is the following: 'Suppose John decides not to buy health insurance anymore, reasoning that he is healthy enough. He calls his mother to report excitedly on his money-saving decision. His mother can berate him for not buying the insurance, by appealing to the fact that he doesn't know that he won't fall ill'. All the examples Stanley gives describe situations in which one criticizes a person's action for not knowing that upon which he bases his decision to perform that action. Therefore, he seems to derive normative claims from a description of what we ordinarily say. Insofar as his claims are normative, what he means is that, if you do not know p but act on the basis of p, your action is not rational.
Now, at one point I asked Stanley: 'Suppose that you come accross a Pyrrhonian skeptic. What would you say to him? Would you tell him (i) that when he acts he is not rational or (ii) that, despite what he says, he does have beliefs and does know lots of things?'. His answer was that the Pyrrhonist does know what he says he doesn't know. It seems that people consider it obvious that Pyrrhonism is not tenable because it is not possible to act on the basis of a reason (I'm using this term loosely) without believing or knowing something. That is, the reason for performing a given action must be a belief or a piece of knowledge. But is it that obvious? It sometimes appears to me that people dismiss Pyrrhonism without carefully reflecting on its conceptual and argumentative resources.