they govern for the advantage not of themselves but of others? Let me ask you a question: Are not the several arts different, by reason of their each having a separate function? And, my dear illustrious friend, do say what you think, that we may make a little progress. Yes, that is the difference, he replied. And each art gives us a particular good and not merely a general one—medicine, for example, gives us health; navigation, safety at sea, and so on? Yes, he said. And the art of payment has the special function of giving pay: but we do not confuse this with other arts, any more than the art of the pilot is to be confused with the art of medicine, because the health of the pilot may be improved by a sea voyage. You would not be inclined to say, would you, that navigation is the art of medicine, at least if we are to adopt your exact use of language? Certainly not. Or because a man is in good health when he receives pay you would not say that the art of payment is medicine? I should not. Nor would you say that medicine is the art of receiving pay because a man takes fees when he is engaged in healing? Certainly not. And we have admitted, I said, that the good of each art is specially confined to the art? Yes. Then, if there be any good which all artists have in common, that is to be attributed to something of which they all have the common use? True, he replied. And when the artist is benefited by receiving pay the advantage is gained by an additional use of the art of pay, which is not the art professed by him? He gave a reluctant assent to this.

Again, I reckon it is the part of law and of right reason to assign to each one what is appropriate to him, and belongs to him, and falls to him. For...