My kindness of the past is not to be my duty of the future; a voluntary favour is not to be turned into an obligation to take unwelcome orders; the principle is not to be established that he who once cures a man is bound to cure any number of others at his bidding ever after. That would be to appoint the patients we cure our absolute masters; _we_ should be paying _them_, and the fee would be slavish submission to their commands. Could anything be more absurd? Because you were ill, and I was at such pains to restore you, does that make you the owner of my art? All this I could have said, if the tasks he imposed upon me had been within my powers, and I had declined to accept all of them, or, on compulsion, any of them. But I now wish you to look further into their nature. 'You cured me of madness (says he); my wife is now mad and in the condition I was in (that of course is his idea); she has been given up as I was by the other doctors, but you have shown that nothing is too hard for you; very well, then, cure her too, and make an end of her illness.' Now, put like that, it sounds very reasonable, especially in the ears of a layman innocent of medical knowledge. But if you will listen to what I have to say for my art, you will find that there _are_ things too hard for us, that all ailments are not alike, that the same treatment and the same drugs will not always answer; and then you will understand what a difference there is between refusing and being unable. Pray bear with me while I generalize a little, without condemning my disquisition as pedantic, irrelevant, or ill-timed.