[B]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?
[C]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?