How does one know one is not dreaming?

Question

How does one know one is not dreaming? How could one logically demonstrate to a skeptic that one is "really" there, awake and not just dreaming the entire situation/world around him? Specifically what I'm asking is: which if any philosophers have addressed this problem of *how* one knows one is or is not dreaming?

Answer 1

"How does one know one is not dreaming?"

Depends on what you mean by 'know'. Some would say that you know p only if your evidence for p, say q, is either self-evident or incorrigible, and you know q, and it's not possible that q is true and p is false. In other words, you know p only if p admits of no doubt whatever. On this view, unless you're sensing something (e.g., a color, a shape, a sound, a taste, a smell) that you couldn't sense if you were dreaming, then you don't know you're not dreaming.

On the other hand, some would say that, in some cases, you can know p so long as you believe p, p is true, and you believe p because it was brought about by your cognitive equipment interacting with its environment in the right kind of way--even if you're in no position to "see" whether your cognitive equipment is interacting with its environment in the right kind of way. On this view, if you're not dreaming, and you believe you're not dreaming, and your belief that you're not dreaming was brought about by your cognitive equipment interacting with its environment in the right kind of way, then you know that you're not dreaming.