The present study is an extended exploration of the manner in which the western church developed the Pauline concept of ‘justification’ throughout two thousand years of reflection and debate. It reflects my own interest over four decades in a number of areas of scholarship, especially the intellectual origins of the European Reformation of the sixteenth century, and the nature of doctrinal development within the Christian tradition. It can be seen as both a celebration and criticism of the pioneering work of Albrecht Benjamin Ritschl, Die christliche Lehre von der Rechtfertigung und Versöhnung (1870). While this earlier work remains a landmark of scholarship in the field, its clear theological precommitments and prejudices undermine the reliability of its scholarship, and thus reduce its value to the theological community. In writing this book, I have tried to set my own confessional partialities and theological commitments to one side, aiming to present a scholarly and unbiased account of the history of this important doctrine.