STRANGER: And that which exchanges the goods of one city for those of another by selling and buying is the exchange of the merchant?
THEAETETUS: To be sure.
STRANGER: 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.
THEAETETUS: What do you mean?
STRANGER: You want to know what is the meaning of food for the soul; the other kind you surely understand.
THEAETETUS: Yes.
STRANGER: 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?
THEAETETUS: To be sure he may.
STRANGER: 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?
THEAETETUS: Certainly I should.