“Why does the cycle move as it does? What causes these periodic alternations, this ebb and this flow, in the national priorities? If it is a genuine cycle, the explanation must be primarily internal. Each phase must flow out of the conditions – and contradictions – of the phase before and then itself prepare the way for the next recurrence. A true cycle is self-generating. It cannot be determined, short of catastrophe, by external events. Wars, depressions, inflations may heighten or complicate moods, but the cycle itself rolls on, self-contained, self-sufficient and autonomous. . .The roots of cyclical self sufficiency lies 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.”
Arthur M. Schlesinger, Jr.
The Cycles of American History