This chapter explains the meaning of the term ‘scientific law’ and shows that the concept of causation need not be replaced by that of law but on the contrary often actually enters into it. It presents a cursory examination of both causal and noncausal types of scientific law; and argues that causal laws are only a species of the genus scientific law. Following an ancient tradition recorded by Sextus Empiri-cus, lawfulness—that is, agreement with law—is usually identified with causality, as if no other kinds of scientific law were possible than causal laws. Statistical laws are indisputably noncausal, even though some of them may be shown to be partly derivable from laws having a causal component. Historical laws are enormously more complex than natural laws. One of the difficulties besetting the disclosure of laws in any field is the low frequency of observed regularities.