DEMONIC ARGUMENTS

Some arguments for ignorance go like this: (1) N knows that P entails Q; (2) For any person S and any propositions p and q, if S knows that p, and

knows that p entails q, then he knows that q; (3) N does not know that Q;

So: (4) N does not know that P. This chapter is about (1)–(4) arguments in which Q stands for the negation of

(D) Nothing exists but N and a demon who makes him believe whatever it is that in the actual world he does believe,

and P stands for some contingent proposition which entails the negation of (D). Such arguments I call demonic.