“According to this reasoning,” says my opponent, “you would say that you owe nothing to a physician beyond his paltry fee, nor to your teacher, because you have paid him some money; yet these persons are all held very dear, and are very much respected.” In answer to this I should urge that some things are of greater value than the price which we pay for them. You buy of a physician life and good health, the value of which cannot be estimated in money; from a teacher of the liberal sciences you buy the education of a gentleman and mental culture; therefore you pay these persons the price, not of what they give us, but of their trouble in giving it; you pay them for devoting their attention to us, for disregarding their own affairs to attend to us: they receive the price, not of their services, but of the expenditure of their time. Yet this may be more truly stated in another way, which I will at once lay before you, having first pointed out how the above may be confuted. Our adversary would say, “If some things are of greater value than the price which we pay for them, then, though you may have bought them, you still owe me something more for them.” I answer, in the first place, what does their real value matter, since the buyer and seller have settled the price between them?