The New Evil Demon Problem and the Nature of Evidence

This chapter explores the challenge that the New Evil Demon Problem poses for so-called “externalist” theories of evidence. It argues that the best view of evidence is a liberalized form of externalism. According to that view, paradigmatic evidence in the sciences and elsewhere includes publicly known facts about the external world, evidence that we would not have in a hypothetical scenario in which we are the victims of radical deception. On the other hand, our evidence is not limited to our knowledge, and for this reason, even radically deceived thinkers are often in a position to have justified beliefs about their environment. Given the radical diversity of topics about which we can have justified beliefs, and the extremely wide range of circumstances in which it's possible for us to hold such beliefs, we should embrace the idea that even radically different things can play the justifying role of evidence.