To become aware of what is constant in the flux of nature and life is the first step in abstract thinking. The recognition of regularity in the courses of the heavenly bodies and in the succession of seasons first provides a basis for a systematic ordering of events, and this knowledge makes possible a calendar. ... Simultaneously with this concept, a system of relationships comes into the idea of the world. Change is not something absolute, chaotic, and kaleidoscopic; its manifestation is a relative one, something connected with fixed points and a given order.
