 What are laws of nature? Well, on a regularity theory of causation, a law is a regularity understood as a stable pattern of events—nothing more, nothing less. And yet, laws are still special regularities. According to Mill (1843), regularities which subsume other true regularities are more general than the subsumed ones. The laws of nature are those regularities which are the most general. They thus organise our knowledge of the world in an ideal deductive system which strikes the best balance between simplicity and strength (see, e.g., 1843: Book III, Ch. XII). This best system account of laws has been further developed by Ramsey and Lewis. Ramsey puts it as follows,