The Nazi regime championed an ideology of human inequality designed to assure the health and purity of the German national community. Membership in the community was to be based on biology; race and not culture was to determine inclusion. It thus became the official policy of the German state to exclude those considered to be a threat to the nation's health and purity. This exclusion was based on biology and directed against groups of human beings considered alien or inferior; heredity determined the fate of groups and individuals.
Although the campaign against supposedly alien influences was directed against large numbers of human beings classified as incompatible with the Nordic ideal of "Aryan" Germans—for example, persons of African or Oriental descent—only two so-called alien groups resided in Central Europe in sufficient numbers to require the intervention of the state: Jews and Gypsies. Against them the Nazi regime inaugurated a concerted policy of isolation, discrimination, and repression. Their isolation culminated in the Nuremberg racial laws of September 1935, which prohibited marriages between Germans and members of the proscribed groups; it also made any sexual contact between them illegal and punishable by death. During the 1930s, the exclusion of Jews involved, in addition to isolation and marginalization, the drive to force them to leave the country, and exclusion of Gypsies —that is, Sinti and Roma—involved their incarceration in so-called Gypsy camps. During the war, the German state practiced a far more radical form of exclusion, the mass murder of all members of the excluded groups, applying the so-called final solution of the Jewish and Gypsy question in every European country occupied by or allied with Germany.
A long tradition of anti-Semitism in Christian Europe had laid the groundwork for the popular acquiescence to the isolation of the Jews. But only the transformation of religious into racial anti- Semitism during the nineteenth century made possible the exclusion of Jews regardless of their commitment to German culture. Their heredity, and not their culture, determined their fate. The same applied to the Gypsies. As a result of the American and French revolutions, previously repressed minorities, including Jews and Gypsies, had been granted citizenship during the nineteenth century, but the equality engendered by emancipation had been challenged by the rise of scientific theories of race that opposed the absorption of the outsiders.
The disabled made up the third target of the Nazi policy of exclusion. Alongside Jews and Gypsies, human beings with physical or mental disabilities designated as "unfit" were also to be eliminated from the German national community. They too faced a long tradition of prejudice , which in the nineteenth century had as well been transformed into a racially based theory of their inferiority.
The scientific movement responsible for this harsher view of the disabled was known as eugenics. The term had been coined in 1881 by the British naturalist and mathematician Francis Galton and described by the leading American eugenicist Charles B. Davenport as "the science of the improvement of the human race by better breeding."