Ernest Gellner—a Jew who escaped from Czechoslovakia in 1939 after Hitler invaded—knew first-hand the catastrophic effects of excessive nationalism, and he was determined to understand the phenomenon that had shaped so much of 20th century history. Gellner argued that the concept of 'nation' is not an ancient notion but rather a modern idea born out of the seismic social and cultural shifts that industrialization brought to the Western world. Nationalism, he concluded, was not the same thing as patriotism—it was an unanticipated, toxic by-product of mass literacy, mass education, and mass production.