The Quack Doctor explained simply

A certain man fell sick and took to his bed. He consulted a number of doctors from time to time, and they all, with one exception, told him that his life was in no immediate danger, but that his illness would probably last a considerable time. The one who took a different view of his case, who was also the last to be consulted, bade him prepare for the worst: "You have not twenty-four hours to live," said he, "and I fear I can do nothing." As it turned out, however, he was quite wrong; for at the end of a few days the sick man quitted his bed and took a walk abroad, looking, it is true, as pale as a ghost. In the course of his walk he met the Doctor who had prophesied his death. "Dear me," said the latter, "how do you do? You are fresh from the other world, no doubt. Pray, how are our departed friends getting on there?" "Most comfortably," replied the other, "for they have drunk the water of oblivion, and have forgotten all the troubles of life. By the way, just before I left, the authorities were making arrangements to prosecute all the doctors, because they won't let sick men die in the course of nature, but use their arts to keep them alive. They were going to charge you along with the rest, till I assured them that you were no doctor, but a mere impostor."