Arnold Clapmarius (1574–1604) became Professor of History and Political Science in 1600 at the Academy later University of Altdorf near Nürnberg. His main work ›De Arcanis Rerumpublicarum‹ – by no means a guide or manual on clandestine politics, but an early enlightened text about the mechanisms of politics in monarchical, aristocratical or democratical rule – was printed in eight editions throughout the 17th century. The number of issues shows the importance of this text during the religious controversies and constitutional conflicts in the period around the Thirty Years‹ War: Clapmarius first presents a system of the power by the government and the affairs of state and by that he is first in the foundation of public law, so he is regarded as precursor in the thinking about state under the rule of law. It is overdue to include this work in the canon of texts about the history of political ideas in the early modern era.