sophist   

Str. The nature of the other appears to me to be divided into
fractions like knowledge.
Theaet. How so?
Str. Knowledge, like the other, is one; and yet the
various parts of
knowledge have each of them their own particular name, and
hence there
are many arts and kinds of knowledge.
Theaet. Quite true.
Str. And is not the case the same with the parts of the
other, which
is also one?
Theaet. Very likely; but will you tell me how?
Str. There is some part of the other which is opposed to the
beautiful?
Theaet. There is.
Str. Shall we say that this has or has not a name?
Theaet. It has; for whatever we call not beautiful is
other than the
beautiful, not than something else.
Str. And now tell me another thing.
Theaet. What?
Str. Is the not-beautiful anything but this-an existence parted
off from a certain kind of existence, and again from another point
of view opposed to an existing something?
Theaet. True.
Str. Then the not-beautiful turns out to be the opposition of
being to being?
Theaet. Very true.
Str. But upon this view, is the beautiful a more real and the
not-beautiful a less real existence?
Theaet. Not at all.
Str. And the not-great may be said to exist, equally with
the great?
Theaet. Yes.
Str. And, in the same way, the just must be placed in the same
category with the not-just the one cannot be said to have any more
existence than the other.
Theaet. True.
Str. The same may be said of other things; seeing that the
nature of
the other has a real existence, the parts of this nature must
equally be supposed to exist.
Theaet. Of course.
Str. Then, as would appear, the opposition of a part of the other,
and of a part of being, to one another, is, if I may venture to say
so, as truly essence as being itself, and implies not the opposite
of being, but only what is other than being.
Theaet. Beyond question.
Str. What then shall we call it?
Theaet. Clearly, not-being; and this is the very nature for which
the Sophist compelled us to search.
Str. And has not this, as you were saying, as real an existence as
any other class? May I not say with confidence that not-being has an
assured existence, and a nature of its own? just as the great was
found to be great and the beautiful beautiful, and the not-great
not-great, and the not-beautiful not-beautiful, in the same manner
not-being has been found to be and is not-being, and is to
be reckoned
one among the many classes of being. Do you, Theaetetus, still feel
any doubt of this?
Theaet. None whatever.
Str. Do you observe that our scepticism has carried us beyond the
range of Parmenides' prohibition?