This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book explores a number of the moral codes which inspired, justified and sustained the resisting conscience in the Third Reich. It argues that the position of the churches was characterised by ‘fluctuations, ambivalences, and even contradictions’. The work of the historian must rest squarely on the evidence which the past has bequeathed. The moral imperative of resistance is difficult to measure because it is often disguised behind the claims of practical, institutional realism. The broad mandates of religious faith do not have a clear place in such a culture. The subtlety with which distinct Christian principles could merge, sometimes almost imperceptibly, into other values, philosophical, political or patriotic, is striking and significant. An age which was conscious of nationhood was the more likely to find the idea of a people without a nation a judgement of God.