Most of the time, epistemologists take it for granted that people have a lot of knowledge about the world around them. I know that the Earth orbits the sun, that Kennedy was assassinated in 1963, that my cat likes milk, and so on. Philosophical skeptics, however, argue that we don’t really know many of the things we normally think we know. The most extreme skeptics say that nobody knows anything at all. A slightly less extreme form of skepticism, external world skepticism, holds that nobody knows anything about the external world (the world outside of one’s own mind). According to this view, then, I don’t really know any of the things I just said I did.