Sarah asked:

How do I know I am not dreaming?

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The problem is this: For any thing I experience it is possible that I may also dream I experience it and
if I am dreaming X I am not really doing X. So 1 cannot be certain that I am doing X if I cannot be
certain that I am not dreaming that I am doing X.

But there is no way to distinguish dreaming X from really doing X, so I cannot be certain that I am not
dreaming X.

There are three possible ways to get out of this troubling situation. Option one is to question the
premise that there is no way to distinguish dreams from waking life. Option two is to question the idea
that it is possible to dream everything, perhaps there are some things that we cannot dream. That
way, if we experience them we know that we are awake. Option three is to question the 'epistemic'
condition that to know X we must know the falsity of all the things incompatible with knowing X.

I think that the first two options fail and so we are forced to find a conception of knowledge that avoids
the epistemic condition. Option one fails because if we have some test that we can apply to
discriminate between dreams and waking life it is always possible to dream that we have applied the
test and so we would never know if it has been successful. Descartes thought that the difference was
that waking life is joined together by memories unlike dreams. But surely it is possible for dreams to
be connected by memories, or, if not, then at least for us to dream that they are!

Option two fails for similar reasons, say, for example that "I am now asleep and having a dream" is
not something that we can know when we are actually dreaming (since we cannot know anything
when we are dreaming). So if and when we experience it, we know that we are in fact awake! But it is
still possible to dream that we are asleep and so once again we cannot tell whether we really know
we are awake or merely dreaming that we know we are awake.

So by elimination we have to adopt option three, unfortunately 1 do not have anything positive to say
about this yet.

Brian Tee
Dept of Philosophy
University of Sheffield.

Second opinion:

Logically you do not know you are not dreaming since any evidence that you are not could be dreamt,
including being told and pinched. The problem is the sceptical problem and is not answerable
logically.

However, you do know that you are not dreaming in the same way you know that you are not insane.
To really have a concern that you might be dreaming is rather akin to insanity, in that you have begun
to lose a basic sense of reality. This is a psychological rather than philosophical problem.

A grasp of reality requires a conscious rather than unconscious state. Indreams, as in insanity, the
unconscious takes over.

Rachel Browne