 Second, historians often want to answer “why” questions: “Why did this event occur? What were the conditions and forces that brought it about?” What were the motivations of the participants? This body of questions invites the historian to provide an explanation of the event or pattern he or she describes: the rise of fascism in Spain, the collapse of the Ottoman Empire, the occurrence of ethnic cleansing in Bosnia in 1992 and later. And providing an explanation requires, most basically, an account of the causal mechanisms, background circumstances, and human choices that brought the outcome about. We explain an historical outcome when we identify the social causes, forces, events, and actions that brought it about, or made it more likely.