Character of [general] principles [in science]

Examples of principles that can be viewed in several ways include the Principle of Entropy Increase (Second Law of Thermodynamics), the Principle of Relativity, Newton's Laws, the Uncertainty Principle and the Principle of Natural Selection. The Principle of Entropy Increase, for example, is partly a law of nature relating to properties of heat, partly an abstract fact about ensembles of dynamical systems, and partly a foundation for the definition of entropy. In this case and in others, however, the most important role of a principle is as a guide to intuition and understanding.