A great man lays upon posterity the duty of understanding him. The task is not easy even with those well-defined, four-square personalities, who belong to a recognizable type, whose purpose was single and whose career was the product of obvious causes; for we have still in our interpretation to recover an atmosphere which is not our own. It is harder when the man in question falls under no accepted category, and in each feature demands a new analysis. It is hardest of all with one who sets classification at defiance, and seems to unite in himself every contrary, who dominates his generation like some portent of nature, a mystery to his contemporaries and an enigma to his successors. In such a case his interpreter must search not only among the arcana of his age, its hidden forces and imponderable elements, but among the profundities of the human spirit.