This article explores different forms of openness and closure in two knowledge communities: the fictional world of Castalia in Hermann Hesse's great work "The Glass Bead Game", and the twenty-first-century cyberspatial universe of Wikipedia. These two worlds differ in some important respects, but they also share a number of educationally significant features in common. The authors compare the respective approaches to knowledge, decision-making and social organization in Castalia and Wikipedia. They argue that both can be seen as flawed knowledge communities, from which, nonetheless, much can be learned that is helpful in advancing current discussions of openness as an ideal.