Of late years, the need for fresh changes in method has become plain. Christopher Columbus Langdell, the inventor of the case-system, laid down two fundamental propositions: “First, that law is a science; second, that all the available materials of that science are contained in printed books.” Experience has proved that he was right in believing that attendance in a lawyer’s office or at the proceedings of courts was not essential to a legal education. But the scope of legal study must now extend beyond printed books, certainly beyond law books. Since law is not an isolated department of knowledge, but a system of rules for the regulation of human life, the truth of those rules must be tested by many facts outside the past proceedings of courts and legislatures. Not only law in books but law in action has to be considered, and after learning the principles evolved by a process of inclusion and exclusion in the decisions or by intermittent legislative action, the scholar must find how those principles actually work in the bank, the factory, the street, and the jail. The problem is still debated, whether this can better be done in the pre-legal college course or by the use of non-legal experts in the law schools, or whether the necessary material should be assimilated and presented by the law teachers themselves. Yet this widening of the content of legal study does not in the least impair the validity of Langdell’s method, the systematic investigation of the sources of law at first hand, whether those sources be found in the reports and statutes which he had in mind, or in the economic, social, and psychological facts which have demanded attention in recent years.