My task would be endless if I tried to collect more instances to prove that valuable things are sold at a low price. What, then? Why is it that I owe something more to my physician and my teacher, and yet do not complete the payment of what is due to them? Because from being physician and teacher they pass into friends, and we are under obligation to them, not because of their skill, which they sell, but because of their kindly and friendly goodwill. If, therefore, a physician does nothing more than feel my pulse, and put me on the list of those whom he visits in his rounds, instructing me what to do or to avoid without any personal feeling, I owe him nothing more than his fee, because he views me, not as a friend, but as a commander.6 Nor is there any reason why I should venerate a teacher if he has considered me merely one of his many pupils, and has not deemed me worthy of any particular and special consideration, if he has not directed his attention to me, but has allowed me, not so much to learn from him, as to pick up any knowledge that he spilled into our midst. What reason, then, do we have for being much indebted to them? It is, not that what they have sold is worth more than we paid for it, but that they have contributed something to us personally. Suppose a physician gave me more attention than was professionally necessary; that it was, not for his professional reputation, but for me, that he feared; that he was not content to indicate remedies, but also applied them; that he sat at my bedside among my anxious friends, that he hurried to me at the crises of my illness; that no service was too burdensome, none too distasteful for him to perform; that he was not indifferent when he heard my moans; that, though a host of others called for him, I was always his chief concern; that he took time for others only when my illness had permitted him — such a man has placed me under obligation, not as a physician, but as a friend. Suppose, again, that the other endured labor and weariness in teaching me; that, besides the ordinary sayings of teachers, there are things which he has transmitted and instilled into me; that by his encouragement he aroused the best that was in me, at one time inspirited me by his praise, at another warned me to put aside sloth; that, laying hand, so to speak, on my mental powers that then were hidden and inert, he drew them forth into the light; that, instead of doling out his knowledge grudgingly in order that there might be the longer need of his service, he was eager, if he could, to pour the whole of it into me — if I do not owe to such a man all the love that I give to those to whom I am bound by the most grateful ties, I am indeed ungrateful.