law of nature

Scientific generalization that both explains and predicts physical phenomena; laws of nature are generally assumed to be descriptive of, and applicable to, the world. The three laws of thermodynamics are examples.

However, the first of Isaac Newton's laws of motion discusses the behaviour of a moving body not acted on by a net force, and this neither applies to the world nor describes it, because there are no such bodies. Hence, some philosophers of science have argued that the laws of nature are rules governing scientists' expectations and so are prescriptive rather than descriptive. Others have argued that laws are idealized descriptions to which the world approximates, as triangles on a blackboard approximate to Euclidean triangles.