Carman asked:

My teacher give me an assignment. This is what we are asked to imagine: In the morning, I am a
student. My daytime experience is continuous. While in my dream, the things I do are continuous too,
such as if I am a singer, I will see myself singing tonight and on the next night I see myself singing
and continue to do other things too.

In this situation, can I explain that there are two "mines" but which one is the real mine, I do not know.
You may say I feel pain when I am in reality but in the dreams I won't! I doubt that our brain controls
our sensation and it can give us the signal and the feeling of pain when we are sleeping too, therefore
I would like to say I cannot distinguish which "mines" are real and then I will become crazy! Can I say
it in that way??

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The kind of scenario you are describing was first discussed in a well known paper by Anthony
Quinton 'Spaces and Times' (Philosophy1962).

Quinton's solution is to say that there are not two 'yous', but rather one you living in two spatially
unrelated worlds, the world where you are a philosophy student, and the world where you are a
singer. Quinton uses this thought experiment as a way of testing Kant's argument in the Critique of
Pure Reasonthat experience is only possible on the condition that I am able to interpret it as
experience of a spatially unified world. In other words, according to Kant there can only be one space.

As you say, both worlds are equally continuous and coherent. When you go to sleep in one world,
you wake up in the other. In both worlds, you feel pleasure and pain. There is not the slightest
indication that one world is only a dream while the other is real.

I am not sure that Quinton has succeeded in making his case against Kant. I am worried by the idea
there seems to be no criterion for the truthfor the things you claim to remember about your
adventures as a singer, while you are living the life of a student, or for the things you claim to
remember about your student existence, while you are in the world of the singer. In either case, the
other life might as wellbe a dream. You can call each alternative world a 'dream' in turn and never be
proved wrong by things that happen in the world you are currently in.

The interesting idea that there are two yous, rather than one you living in two worlds, might arise in
the following way. Suppose that as a student, you are quite nervous and shy, while as a singer you
are exuberant and full of charisma; or suppose that as a student you have high standards of moral
integrity, while as a singer you live a life of drug taking and debauchery. In our dreams, we some
times seem to become different 'persons', and this does not pose a problem. If the two worlds are
equally real, however, then the problem becomes acute. Even so, it is one and the same 'you' who
experiences, and remembers, both lives.

Geoffrey Klempner