The article restates the theory of Nationalism, which it links to the transition from agrarian to industrial or industrializing society. In an agrarian society, culture is used to underscore a complex and fairly stable system of statuses. Political units themselves are complicated and overlapping and ill-defined, and culture does not demarcate their boundaries. In an industrial society, work ceases to be physical and becomes semantic, and society itself is highly mobile. Under these circumstances, a shared and standardized, codified culture, inculcated by formal education, becomes a precondition of social participation and employability. When shared, literacy-linked culture is very important, people identify with it and thus become ‘nationalists’. The article also traces the five stages which Europe has passed in the course of this transition: the perpetuation of the old dynastic/religious political system in 1815, the century of nationalist irredentism, the setting up of a political system in 1918 based on nationalities which was weak and self-defeating, the most intensive period of ‘ ethnic cleansing’ in the 1940s under the cover of war-time secrecy and post-war retaliation, and finally a certain demolition of the intensity of ethnic feeling during advanced industrialism, thanks to the partial convergence of industrial cultures and the softening impact of affluence.