The Story of Philosophy

by Will Durant

We may perhaps approach such a principle by trying to unify the highest generalizations of physics. These are the indestructibility of matter, the conservation of energy, the continuity of motion, the persistence of relations among forces (i.e., the inviolability of natural law), the transformability and equivalence of forces (even of mental and physical forces), and the rhythm of motion. This last generalization, not usually recognized, needs only to be pointed out. All nature is rhythmical, from the pulsations of heat to the vibrations of violin strings; from the undulations of light, heat and sound to the tides of the sea; from the periodicities of sex to the periodicities of planets and comets and stars; from the alternation of night and day to the succession of the seasons, and perhaps to the rhythms of climatic change; from the oscillations of molecules to the rise and fall of nations and the birth and death of stars.