that madmen or dreamers think truly, when they
imagine, some of them that they are gods, and others that they can fly,
and are flying in their sleep.

SOCRATES: Do you see another question which can be raised about these
phenomena, notably about dreaming and waking?

THEAETETUS: What question?

SOCRATES: A question which I think that you must often have heard
persons ask:--How can you determine whether at this moment we are
sleeping, and all our thoughts are a dream; or whether we are awake, and
talking to one another in the waking state?

THEAETETUS: Indeed, Socrates, I do not know how to prove the one
any more than the other, for in both cases the facts precisely
correspond;--and there is no difficulty in supposing that during all
this discussion we have been talking to one another in a dream; and when
in a dream we seem to be narrating dreams, the resemblance of the two
states is quite astonishing.

SOCRATES: You see, then, that a doubt about the reality of sense is
easily raised, since there may even be a doubt whether we are awake
or in a dream. And as our time is equally divided between sleeping
and waking, in either sphere of existence the soul contends that the
thoughts which are present to our minds at the time are true; and during
one half of our lives we affirm the truth of the one, and, during the
other half, of the other; and are equally confident of both.

THEAETETUS: Most true.

SOCRATES: And may not the same be said of madness and other disorders?
the difference is only that the times are not equal.

THEAETETUS: Certainly.

SOCRATES: And is truth or falsehood to be determined by duration of
time?

THEAETETUS: That would be in many ways ridiculous.

SOCRATES: But can you certainly determine by any other means which of
these opinions is true?

THEAETETUS: I do not think that I can.

SOCRATES: Listen, then, to a statement of the other side of the
argument, which is made by the champions of appearance. They would say,
as I imagine--Can that which is wholly other than something, have the
same quality as that from which it differs? and observe, Theaetetus,
that the word 'other' means not 'partially,' but 'wholly other.'

THEAETETUS: Certainly, putting the question as you do, that which is
wholly other cannot either potentially or in any other way be the same.

SOCRATES: And must therefore be admitted to be unlike?

THEAETETUS: True.

SOCRATES: If, then, anything happens to become like or