 Every period presents challenges for the historian, and every period raises problems for historiography and the philosophy of history. The twentieth century is exceptional, however, even by this standard. Events of truly global significance occurred from beginning to end. War, totalitarianism, genocide, mass starvation, ideologies of murder and extermination, and states that dominated their populations with unprecedented violence all transpired during the century. The Holocaust (Snyder 2010, 2015), the Holodomor (Applebaum 2017), the Gulag (Applebaum 2003), and the cultural and ideological premises of the Nazi regime (Rabinbach et al 2020) have all presented historians with major new challenges of research, framing, and understanding. How should historians seek to come to grips with these complex and horrifying circumstances? These occurrences were highly complex and extended and often hidden: many thousands of active participants, many groups and populations, millions of victims, conflicting purposes and goals, new organizations and institutions, numerous ideologies. Moreover, through too many of these novelties is woven the theme of evil – deliberate destruction, degradation, and murder of masses of innocent human beings. The historian of virtually any aspect of the twentieth century is confronted with great problems of frame-setting, explanatory purpose, and moral reflection.