This presentation examines the contradictions that emerged between universalist ambitions and three historical processes: categorization, segregation, and extermination. In studying the societies of the late Middle Ages and the Early Modern era, the question arises of the incompatibility between, on the one hand, Saint Paul’s message (“There is neither Jew nor Greek, there is neither slave nor free man, there is neither male nor female, for you are all one in Christ Jesus.” Galatians [3-28]”), and rules of segregation founded upon an assertion of natural inferiority and the inability of people to change, on the other. The most salient case in Early Modern Europe was the fate of the descendants of converts in Iberian societies, branches of families that had been Jewish or Muslim, before those faiths were outlawed. The contradiction between universalism (of which Catholicism is the bearer by definition) and the confinement of persons and groups into racialized categories of belonging is not unique in European history. For the purposes of experimentation, I would like to put this argument of an ideological antinomy to the test by examining other examples until modern times.