Historians are usually more at ease telling stories that have clear endings, such as those that describe ancient Egyptian civilization, Chinese maritime voyages, the collapse of the Aztec Empire, or the French Revolution. There is a finality to these stories and a distance from them that makes it easier for historians to assume the posture of detached observers, even if their understandings of those events change over time. Finality, distance, and detachment are harder to come by when historians are describing the events of the past century, for many of its processes are clearly not over. The United States’ role as a global superpower and its wars in Iraq and Afghanistan, the fate of democracy in Latin America and the Arab world, the rise of China and India as economic giants, the position of Islam in Turkey and Iran—all of these are unfinished stories, their outcomes unknown and unknowable. In dealing with such matters, historians write from the middle of the stream, often uncomfortably, rather than from the banks, where they might feel more at ease.

In part, that discomfort arises from questions about the future that such issues inevitably raise. Can the spread of nuclear weapons be halted? Will democracy flourish globally? Are Islamic and Christian civilizations headed for a global clash? Can African countries replicate the economic growth experience of India and China? Historians in particular are uneasy about responding to such questions because they are so aware of the unexpectedness and surprising quality of the historical process. Yet those questions about the future are legitimate and important, for as the nineteenth-century Danish philosopher Søren Kierkegaard remarked, “Life can only be understood backward, but it is lived forward.” History, after all, is the only guide we have to the possible shape of that future. So, like everyone before us, we stumble on, both individually and collectively, largely in the dark, using analogies from the past as we make our way ahead.

These vast uncertainties about the future provide a useful reminder that although we know the outcomes of earlier human stories—the Asian and African struggles for independence, for example—those who lived that history did not. Such awareness can perhaps engender in us a measure of humility and greater sympathy with those whose lives we study. However we may differ from our ancestors across time and place, we share with them an immense ignorance about what the future holds.