Catholic Church challenged lay rulers’ hold over the appointment of bishops. This eleventh-century rupture sundered religious and lay power, and meant that European emperors, kings, and princes henceforth had to tread a fine line: caught between the opposition they encountered from strong social groups such as townsmen, nobles, and Catholic clergy and from other European rulers.  What Karl Marx dismissively referred to as the “medieval rubbish” nurtured the seeds of modern Europe – the modern state, the modern market economy, and modern democracy – by creating power pluralism between and within political units. Jørgen Møller has a PhD from the European University Institute in Florence, Italy, and is currently professor of Political Science at Aarhus University. His research focuses on European history. He has published books about the role of the Catholic Church in European state formation and about the politics of succession. He is also the author of books on international relations and democracy and democratization.