"It is of course not sufficient to appeal to the authority of Marx, Hegel, or any of their contemporaries follower to establish the validity of the direction of History. In the century and a half since they wrote, their intellectual legacy has been relentlessly assaulted from all directions. The most profound thinkers of the twentieth century have directly attacked the idea that history is a coherent of intelligible process; indeed, they have denied the possibility that any aspect of human life is philosophically intelligible."