Arthur M. Schlesinger Jr. writes: A true cycle … is self-generating. It cannot be determined, short of catastrophe, by external events. War, depressions, inflations, may heighten or complicate moods, but the cycle itself rolls on, self-contained, self-sufficient and autonomous…. The roots of this cyclical self-sufficiency lie deep in the natural life of humanity. There is a cyclical pattern in organic nature—in the tides, in the seasons, in night and day, in the systole and diastole of the human heart.
