The Enlightenment faith in the power of reason and the inevitability of human progress increasingly came under attack in the late nineteenth century. Scientific advances, technological innovation, and increased productive capacity had not led to dramatic social progress. In the view of critics of Enlightenment rationalism like Friedrich Nietzsche and Sigmund Freud, the fact that the march of civilization had not, apparently, civilized human beings, pointed toward the need for new models of human behavior, models that gave more weight to instincts, emotions, and irrationality. While the beginnings of twentieth-century cultural and intellectual trends can be found in the late nineteenth century, the true turning point was World War I. The unprecedented death and destruction of the Great War shook Europeans’ confidence in rationality and progress to the core. For many, after the events of 1914–1919, the world would never be the same. This feeling of fundamental disruption was heightened by the continuing tensions between the combatants over the terms of the peace. It was against this backdrop of uncertainty and disorientation, that the world was plunged into depression in the 1930s. When the Great Depression (1929–1939) hit the United States, the subsequent worldwide financial crisis forced many Europeans to reconsider their most basic beliefs about economic, political, and social relationships. ■