In a normal classroom the teacher has to teach many different students at a time. But no teacher teaches one individual student at a time. His response has to be given in the light of all despite their “difference”, “deviation” or “diversity”. Heterogeneity arises as a mode of perception of difference (i.e. deviation from something interpreted as normal(ity). Insofar, heterogeneity is directly linked to the experience of alienation, the state of not-knowing. In this manner, it becomes clear that heterogeneity is nourished by the experience of the stranger. The presentation will first and foremost analyze the construction (and use) of the stranger in European concepts of education. The paper will ask: Who is he and where does he come from? The answer will be provided on a cognitive-cultural and social level. Secondly, the concept of the stranger will be evaluated critically in the light of traditional didaktik (see Hopmann 2007). Thirdly, the concept of the stranger will be re-placed in didaktik to ask for a concept where culture is taught as loosely connection of diversity and difference, as a plurality of affiliations and memberships as well as richness of ways of being.