sophist   

Str. Then now, Theaetetus, his art may be traced as a branch of
the appropriative, acquisitive family-which hunts
animals,-living-land-tame animals; which hunts man,-privately-for
hire,-taking money in exchange-having the semblance of education;
and this is termed Sophistry, and is a hunt after young men of
wealth and rank-such is the conclusion.
Theaet. Just so.
Str. Let us take another branch of his genealogy; for he is a
professor of a great and many sided art; and if we look back at what
has preceded we see that he presents another aspect, besides that of
which we are speaking.
Theaet. In what respect?
Str. There were two sorts of acquisitive art; the one
concerned with
hunting, the other with exchange.
Theaet. There were.
Str. And of the art of exchange there are two divisions, the one
of giving, and the other of selling.
Theaet. Let us assume that.
Str. Next, will suppose the art of selling to be divided into two
parts.
Theaet. How?
Str. There is one part which is distinguished as the sale
of a man's
own productions; another, which is the exchange of the works of
others.
Theaet. Certainly.
Str. And is not that part of exchange which takes place in
the city,
being about half of the whole, termed retailing?
Theaet. Yes.
Str. And that which exchanges the goods of one city for those of
another by selling and buying is the exchange of the merchant?
Theaet. To be sure.
Str. And you are aware that this exchange of the merchant is of
two kinds: it is partly concerned with food for the use of the body,
and partly with the food of the soul which is bartered and
received in
exchange for money.
Theaet. What do you mean?
Str. You want to know what is the meaning of food for the soul;
the other kind you surely understand.
Theaet. Yes.
Str. Take music in general and painting and marionette playing and
many other things, which are purchased in one city, and carried away
and sold in another-wares of the soul which are hawked about either
for the sake of instruction or amusement;-may not he who takes them
about and sells them be quite as truly called a merchant as he who
sells meats and drinks?
Theaet. To be sure he may.
Str. And would you not call by the same name him who buys up
knowledge and goes about from city to city exchanging his wares for
money?
Theaet. Certainly I should.
Str. Of this merchandise of the soul, may not one part be fairly
termed the art of display? And there is another part which is
certainly not less ridiculous, but being a trade in learning must be
called by some name germane to the matter?
Theaet. Certainly.
Str. The latter should have two names,-one descriptive of the sale
of the knowledge of virtue, and the other of the sale of other kinds
of knowledge.
Theaet. Of course.
Str. The name of art-seller corresponds well enough to the latter;