 Hartz believed that the lack of feudalism in America had created a situation in which only one creed, liberalism (in the classic sense), could be tolerated.Since there was no tolerance for collectivist-oriented systems like socialism, if the U.S. economic system were ever again to suffer a catastrophic failure such as that of the Great Depression, the U.S. might be imperiled by the lack of a viable, legitimate alternative such as socialism.Hartz's theories, as articulated in his 1955 book "The Liberal Tradition in America", served the basis for Levin's own ideas.