For the first time in their history, Americans have begun to wonder whether the problems they face might be too much for them. With cities and university torn by riots, with faith in military power and moral purpose depleted in a meaningless war, with social change apparently out of control, confidence in our destinity is shaken. Here is a brilliant analysis of where we are and where we are going by the internationally famous historian and winner, in 1946 and 1966, of the Pulitzer Prize.