Many of the characteristic features of Christendom, which emerged during the era of third-wave civilizations, have had a long life, extending well into the modern era. The crusading element of European expansion was prominent among the motives of Spanish and Portuguese explorers. Europe’s grudging freedom for merchant activity and its eagerness to borrow foreign technology arguably contributed to the growth of capitalism and industrialization in later centuries. The endemic military conflicts of European states, unable to recover the unity of the Roman Empire, found terrible expression in the world wars of the twentieth century. The controversy about reason and faith resonates still, at least in the United States, in debates about the authority of the Bible in secular and scientific matters. The rift between Eastern Orthodoxy and Roman Catholicism remains one of the major divides in the Christian world. Modern universities and the separation of religious and political authority likewise have their origins in the European Middle Ages. Such a perspective, linking the past with what came later, represents one of the great contributions that the study of history makes to human understanding. We are limited and shaped by our histories.

Yet that very strength of historical study can be misleading, particularly if it suggests a kind of inevitability, in which the past determines the future. Knowing the outcome of the stories we tell can be a serious disadvantage, for it may rob the people we study of the freedom and uncertainty that they surely experienced. In 500, few people would have predicted that Europe would become the primary center of Christianity, while the African and Asian expressions of that faith withered away. As late as 1000, the startling reversal of roles between the Eastern and Western wings of Christendom, which the next several centuries witnessed, was hardly on the horizon. At that time, the many small, rural, unsophisticated, and endlessly quarreling warrior-based societies of Western Europe would hardly have borne comparison with the powerful Byzantine Empire and its magnificent capital of Constantinople. Even in 1500, when Europe had begun to catch up with China and the Islamic world in various ways, there was little to predict its remarkable transformation over the next several centuries and the dramatic change in the global balance of power that this transformation produced.

Usually students of history are asked to remember. But forgetting can also be an aid to historical understanding. To recapture the unexpectedness of the historical process and to allow ourselves to be surprised, it may be useful on occasion to forget—or at least set aside—what we know about what happened next and to see the world as contemporaries viewed it.