The ideal of national belonging had from the start created an “us-them” outlook (see "The Growing Appeal of Nationalism" in Chapter 21); after 1871, new supposedly scientific understandings of racial difference added new layers of meaning to this dichotomy. Modern attempts to use race to categorize distinct groups of people had their roots in Enlightenment thought (see "Race and the Enlightenment" in Chapter 16). Now a new group of intellectuals, including race theorists such as Count Arthur de Gobineau and Houston Stewart Chamberlain, claimed that their ideas about racial difference were scientific, based on hard biological “facts” about bloodlines and heredity. In his early book On the Inequality of the Human Races (1854), Gobineau divided humanity into the white, black, and yellow races based on geographical location and championed the white “Aryan race” for its supposedly superior qualities. Social Darwinist ideas about the “survival of the fittest,” when applied to the “contest” between nations and races, drew on such ideas to further popularize stereotypes about inferior and superior races.

The close links between nationalism and scientific racism helped justify imperial expansion, as we shall see in the next chapter. Nationalist racism also fostered domestic persecution and exclusion. According to race theorists, the nation was supposed to be racially pure, and ethnic minorities were viewed as outsiders and targets for reform, repression, and relocation. For many nationalists, driven by ugly currents of race hatred, Jews were the ultimate outsiders, the stereotypical “inferior race” that posed the greatest challenge to national purity.