Most historical causes emerge from mistakes that men make about the world, that is why those historians who were independently prepared to take subjectivity into account make so many mistakes about causes. Perceptions vary in predictable ways with time, and social status; that is why individual sets of minds lend themselves to sociological inquiry. But perceptions vary also with temperament, with unconscious conflicts, with disharmonies among the public sources of perception. An individual incorporates the shapes of his culture, his craft, and his family, but his character is a unique mixture of conformity. He is not a receptacle for external influences, not always an effect but often a cause.