In little things one person says, "I do not like to touch vinegar, it harms my health"; another says, "I cannot bear eating cream, I cannot digest it"; yet another says, "I cannot stand sugar in my tea, I do not like it." For the latter sugar is poison. If he took poison and made it part of his nature, the same poison would become sugar. But by making things foreign to his nature a man makes his nature exclusive, and by becoming exclusive he subjects himself to them in a way. There comes a time when they rule him, a situation in which he is in their power may occur. A person may say for instance, "Quinine is too bitter, I cannot stand it." But when he is in a fever the doctor says that he must take it. The patient dreads it, but his condition forces him to take it.