This new Yearbook is intended to promote international discussion in the field of the sociology of religion. It is not bound to a fixed approach and thus is open to various theoretical and methodological orientations. The editors of this Yearbook agree, however, that it ought to regain that doser connection of the sociology of religion to general sociological theory which has often been missing in recent years. The sociology of religion has fallen victim to a constriction of its theoretical perspectives during the last two or three decades. Thomas Luckmann has pointed out that this constriction can be traced back to the "methodological principle" (methodischer Grundsatz) in recent sociology of religion which opens religious phenomena to scientific approaches - if at all - only in the form of concrete church institutions 1. It may certainly be asked whether this "methodological principle" should be totally repudiated from the outset. At any rate, this principle shows a way to avoid the difficulties arising from the problem of an operational definition of what religion can be in the context of a sociology of religion. Probably this "methodological principle" is even to be seen as some kind of re action against phenomenological approaches to a definition of religion which often remains inadequate from a sociological point of view.