What distinguishes denominational religious education from other subjects at school? This essay determines its crucial characteristic in the distinction between questions that are decidable (already decided) and undecidable (to be decided by myself) in the tension between the requirement to position oneself and the ban on overpowering the pupils/students. Two third grade classroom scenes on the topic of <Moses> serve as case studies to trace this tension in the practice of religious instruction. Thus this essay contributes both theoretical and empirical insights to the question of a «culture» of religious instruction.