Dynamical similarity

The principle of dynamical similarity (derived from theology) is used as a basic for comparison of systems in a situation when only similarities, and not identities, can be established. This situation also exists in comparing biological and social entities. Biologists and sociologists explain processes on the basis of covariance principles, in contrast to the ability of the physicist to use invariance transformations to explain a physical system (recognized as part of a class for which statistical irregularities can be validly averaged out).