Periodicity as symmetry in time

housman

pp. 113-125

in: Emily Rolfe Grosholz, Great circles, Berlin, Springer, 2018

Abstract

Natural systems, like molecules, cells, organisms, solar systems, stars and galaxies, exhibit stability that persists for awhile, and then disperses. Their stability is manifest in geometric forms that are often highly symmetrical, and that express a "low" energetic state in contrast to other more highly excited, unstable possible states of the same system. It is also manifest in the successful accomplishment of functions that allow the system to interact with its environment while maintaining its own integrity. Integrity is once again linked to shape, as well as to periodicity, which—as Bas van Fraassen observes—is symmetry in time (Van Fraassen 1989: 252). It would be a philosophical mistake to conclude either that the stability of natural systems is an illusion (with Heracleitus) or that their dispersal is an illusion (with Parmenides). The things of the world inhabit the middle kingdom between Being and Becoming; in fact, they constitute that middle kingdom.