This document is the revised and significantly expanded text of two public lectures delivered during the summer semester of 1998 as part of the Otto von Freising Guest Professorship at the Catholic University of Eichstätt. The author thanks the Faculty of History and Social Sciences at the Catholic University of Eichstätt for the honorable invitation to hold the endowed chair. In discussions following both lectures, I received numerous valuable insights. I am particularly grateful for suggestions and critiques from Karl Graf Ballestrem, Heinz Hürten, Eckhard Jesse, Jens Luedtke, Leonid Luks, Ferdinand Kramer, Klaus Schubert, and Bernhard Sutor. Any possible errors are solely the responsibility of the author. Creussen, September 1998 Uwe Backes Table of Contents Page Introduction.