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

It is certainly a Biblical and Classical view that there are levels of reality and even our waking state can be called a dream , as in:

Peace, peace! he is not dead, he doth not sleep— He hath awakened from the dream of life— 'Tis we, who lost in stormy visions, keep With phantoms an unprofitable strife...

You can't even ask the question unless you at least theoretically allow that there might be something besides whatever you term 'dreaming'. You can tell the difference between being thirsty and dreaming of drinking a lot of water and when you wake up you are still thirsty and drink real water. You know the difference then

But all in all this is a case of playing with your own sanity

Charles Sanders Peirce — 'Let us not pretend to doubt in philosophy what we do not doubt in our hearts.'

Answer 2

"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.