ER: Do you speak advisedly, or are you carried away at the moment
by the habit of assenting into giving a hasty answer?

THEAETETUS: May I ask to what you are referring?

STRANGER: My dear friend, we are engaged in a very difficult
speculation--there can be no doubt of that; for how a thing can appear
and seem, and not be, or how a man can say a thing which is not true,
has always been and still remains a very perplexing question. Can any
one say or think that falsehood really exists, and avoid being caught in
a contradiction? Indeed, Theaetetus, the task is a difficult one.

THEAETETUS: Why?

STRANGER: He who says that falsehood exists has the audacity to assert
the being of not-being; for this is implied in the possibility of
falsehood. But, my boy, in the days when I was a boy, the great
Parmenides protested against this doctrine, and to the end of his life
he continued to inculcate the same lesson--always repeating both in
verse and out of verse:

'Keep your mind from this way of enquiry, for never will you show that
not-being is.'

Such is his testimony, which is confirmed by the very expression when
sifted a little. Would you object to begin with the consideration of the
words themselves?

THEAETETUS: Never mind about me; I am only desirous that you should
carry on the argument in the best way, and that you should take me with
you.

STRANGER: Very good; and now say, do we venture to utter the forbidden
word 'not-being'?

THEAETETUS: Certainly we do.

STRANGER: Let us be serious then, and consider the question neither
in strife nor play: suppose that one of the hearers of Parmenides was
asked, 'To what is the term "not-being" to be applied?'--do you know
what sort of object he would single out in reply, and what answer he
would make to the enquirer?

THEAETETUS: That is a difficult question, and one not to be answered at
all by a person like myself.

STRANGER: There is at any rate no difficulty in seeing that the
predicate 'not-being' is not applicable to any being.

THEAETETUS: None, certainly.

STRANGER: And if not to being, then not to something.

THEAETETUS: Of course not.

STRANGER: It is also plain, that in speaking of something we speak of
being, for to speak of an abstract something naked and isolated from all
being is impossible.

THEAETETUS: Impossible.

STRANGER: You mean by assenting to imply that he who says something must
say some one thing?

THEAETETUS: Yes.

STRANGER: So