I might go on forever collecting instances to prove that valuable things are sold at a low price. What then? why is it that I owe something extra both to my physician and to my teacher, and that I do not acquit myself of all obligation to them by paying them their fee? It is because they pass from physicians and teachers into friends, and lay us under obligations, not by the skill which they sell to us, but by kindly and familiar good will. If my physician does no more than feel my pulse and class me among those whom he sees in his daily rounds, pointing out what I ought to do or to avoid without any personal interest, then I owe him no more than his fee, because he views me with the eye not of a friend, but of a commander. 153