摘要：This article examines the process whereby legal principle was created in the formative period of the ius commune (1100–1400). It uses a speci?c example from the realm of the law of letting and hiring to argue that distinct phases can be identified in this process. An appreciation of the existence of these phases, in turn, casts new light on the variety of specialized cognitive techniques employed by medieval jurists to transform Roman legal rules into the "common law" of Europe.
