First published in 1954, this book explores the political ideas of the Middle Ages. It covers the period from the investiture struggle to the end of the fifteenth century and provides comprehensive readings of otherwise inaccessible source material. Each chapter begins with an introductory essay on the subject at hand that leads to a number of translated passages, numerous enough to display a variety of opinion and long enough to indicate the process of thought as well as its conclusions. This book is the first of a two volume set and will be useful to teachers and advanced students of political theory and medieval history. Topics discussed in this volume include law, property and lordship, political authority and community.