The 1940s and 1950s brought a climate of opinion to the United States very different from the dominant one of the earlier 1900s. With the new mood came historical interpretations which were in marked contrast to those of Beard and Parrington. Louis Hartz, a historian of political thought at Harvard University, made the most sweeping statement of the differences between American and European history in The Liberal Tradition in America, a sometimes extravagant and difficult, but exceedingly stimulating and important book. He argued that the big questions of European history had from the beginning been resolved for Americans. Hartz suggested that because most Americans took liberalism for granted and because it had seldom if ever confronted serious challenges from the extreme Left or Right, the liberal tradition in America had escaped popular or scholarly scrutiny. The latter were children of Europe, "un-American" to begin with, outside of America, equipped with meaningful Western categories: feudalism, capitalism, liberalism.