The first volume of the ›Studies‹ series deals with the central concepts of »Lex« and »Ius« and their systematic development within the political theory, philosophy, and law of the Middle Ages up to the School of Salamanca. This reconstruction of the specific form of a practical-juridical and politicalnormative body of knowledge in the Middle Ages focuses on the debates concerning the relationship between positive law, natural law and rational law, which shaped the European tradition of law, as well as the development of international normative regime. Among the contributors to this polylingual volume (with texts in German, English and Italian) are: Francisco Bertelloni, Luis Alberto De Boni, Norbert Brieskorn, Orazio Condorelli, Juan Cruz Cruz, John Doyle, Matthias Kaufmann, Jürgen Miethke, Kenneth Pennington, and Merio Scattola.