People live in the present. They plan for and worry about the future. History, however, is the study of the past. Given all the demands that press in from living in the present and anticipating what is yet to come, why bother with what has been? In the first place, history offers a storehouse of information about how people and societies behave. Understanding the operations of people and societies is difficult, though a number of disciplines make the attempt. An exclusive reliance on current data would needlessly handicap our efforts. How can we evaluate war if the nation is at peace—unless we use historical materials? How can we understand genius, the influence of technological innovation, or the role that beliefs play in shaping family life, if we don't use what we know about experiences in the past? The second reason history is inescapable as a subject of serious study follows closely on the first. The past causes the present, and so the future. Any time we try to know why something happened, we have to look for factors that took shape earlier. Sometimes fairly recent history will suffice to explain a major development, but often we need to look further back to identify the causes of change. Only through studying history can we grasp how things change, comprehend the factors that cause change, and understand what elements of an institution or a society persist despite change. History also helps provide identity. Historical data include evidence about how families, groups, institutions and countries were formed and about how they have evolved while retaining cohesion. Studying the history of one's own family is the most obvious use of history, for it provides facts about genealogy and a basis for understanding how the family has interacted with larger historical change. Family identity is established and confirmed. Many institutions, businesses, communities, and social units use history for similar identity purposes. And nations use identity history as well. Histories that tell the national story are meant to drive home an understanding of national values and a commitment to national loyalty.