science.

YOUNG SOCRATES: Yes, we must certainly do again what we did then.

STRANGER: But this, Socrates, is a greater work than the other, of which
we only too well remember the length. I think, however, that we may
fairly assume something of this sort--

YOUNG SOCRATES: What?

STRANGER: That we shall some day require this notion of a mean with a
view to the demonstration of absolute truth; meanwhile, the argument
that the very existence of the arts must be held to depend on the
possibility of measuring more or less, not only with one another, but
also with a view to the attainment of the mean, seems to afford a grand
support and satisfactory proof of the doctrine which we are maintaining;
for if there are arts, there is a standard of measure, and if there is a
standard of measure, there are arts; but if either is wanting, there is
neither.

YOUNG SOCRATES: True; and what is the next step?

STRANGER: The next step clearly is to divide the art of measurement into
two parts, as we have said already, and to place in the one part all the
arts which measure number, length, depth, breadth, swiftness with their
opposites; and to have another part in which they are measured with the
mean, and the fit, and the opportune, and the due, and with all those
words, in short, which denote a mean or standard removed from the
extremes.

YOUNG SOCRATES: Here are two vast divisions, embracing two very
different spheres.

STRANGER: There are many accomplished men, Socrates, who say, believing
themselves to speak wisely, that the art of measurement is universal,
and has to do with all things. And this means what we are now saying;
for all things which come within the province of art do certainly in
some sense partake of measure. But these persons, because they are
not accustomed to distinguish classes according to real forms, jumble
together two widely different things, relation to one another, and to a
standard, under the idea that they are the same, and also fall into
the converse error of dividing other things not according to their real
parts. Whereas the right way is, if a man has first seen the unity of
things, to go on with the enquiry and not desist until he has found all
the differences contained in it which form distinct classes; nor again
should he be able to rest contented with the manifold diversities which
are seen in a multitude of things until he has comprehended all of them
that have any affinity within the bound