A well-known tradition in thought about law says that the rule of law ‒ the governance of law in the world ‒ is secured by one kind of law and only that kind. According to this tradition, the vitally important kind of law is formal legal prescription. A major figure within the formality-affirming tradition is Max Weber, the German legal sociologist. According to Weber, a fundamental axis of distinction among kinds of legal order is the division between formal justice and substantive ‒ nonformal ‒ justice. Weber puts nonformal ‒ ideal ‒ argument under a cloud. He suggests that ideal argument leading to judgment in law, by nature, is not law-like ‒ not regular, consistent, generalizable. Other writers in the Weberian tradition ‒ Franz Neumann on Nazi law, Roberto Unger on modern law ‒ join in disparagement of nonformal law. This disparagement is a mistake. The Weberians are wrong about nonformal ‒ moral ‒ assertion in law. Inside nomological practice, law's ideal aims and law's rules are not at war. In liberal law, the ideal aims invoked in legal argument are formed to fit and justify the rules. In prescriptive accord, the ideals and the rules work together.