This book describes the efforts of King James VI and I to achieve a religious reconciliation among Christians of many persuasions – English Protestants, Lutherans, Calvinists, Roman Catholics, and Greek Orthodox. James saw religious reconciliation as the key to a stable and peaceful Christendom at a time when religious disputes exacerbated the conflicts among states. Despite the mistrust and opposition some of his efforts generated, they brought significant benefits to Britain and the continent.

While this is a study centered on James's ecumenical and irenic ideas and activities – not a political biography, nor a church history of his reign, nor an account of his foreign policy – it is broadly conceived. The book deals with the whole course of James's reign in Scotland and England in order to show how his vision of a reunited Christendom arose, how it developed in the context of domestic and foreign events, what various statesmen, scholars, and theologians contributed to it, and how he applied that vision to specific political and religious problems. The onset of a European war in the last part of James's reign thwarted his hopes for achieving a lasting peace, but in that crisis he came closer to attaining his objectives than is generally recognized. This book puts several aspects of James's reign in a new perspective: his foreign policy, his relations with the papacy, his part in the controversy over the Oath of Allegiance, his friendship with leading European intellectuals, his interest in the Greek East, his close relations with leaders of Protestant churches abroad, and his peace diplomacy in the early years of the Thirty Years' War.