1,700 years ago, the Roman emperors Constantine and Licinius granted religious freedom – also and particularly for Christianity. The religious policy of Constantine is often associated with the modern ideal of tolerance. This book inquires into the correctness and limitations of this label through a close historical study of this concept and with particular attention to the forms of religious tolerance in Late Antiquity. One important feature of this study is its focus on the reception of Constantine's religious policy from the Reformation era until modern times.