The authors argue that the ideas found in the harder versions of multiculturalism have already been supported by the mid-20th century social-cultural anthropology - both in the scholarly works and in the political activism of its proponents. This form of cultural relativism, making the leap from anthropological method to ontological claims about the organic essence of cultures, is hereby named “culturalism”. By this notion the authors understand a theory of culture that includes central anthropological ideas: a culture precedes and determines individuals belonging to it; cultures have unlimited freedom to generate differences, uninhibited by any human nature; cultures form closed, organic units where all their different articulations, from gastronomy to theology, form an unbreakable whole which implies that these value systems are unique and in no way may be compared with, or judged against, other value systems. Cultural relativism formulated in the American anthropology of the 1940’s and onwards is far from being a simple doctrine. It consists of a whole cluster of loosely connected facts, axioms, propositions, ranging from the completely unproblematic, to strongly problematic and even hardly understandable ideas. All those statements have been critically scrutinized in this paper.