What are the mechanisms underlying the reproduction and change of collective beliefs? The paper suggests that a productive and promising approach for dealing with this question can be found in ontogenetic and cross-cultural studies on ‘collective argumentations and belief systems’; this is illustrated with regard to moral beliefs: After a short discussion of the rationality/relativity issue in cultural anthropology some basic elements of a conceptual framework for the empirical study of collective argumentations are outlined. A few empirical case studies are (...) summarized; the results deliver some empirical evidence to the assumption that as the ‘logic of collective argumentations’ develops in children and adolescent there will be different and increasingly more complex constraints on the kinds of basic moral beliefs that can be collectively accepted. Most importantly, as children approach adolescence they may have acquired a ‘logic of argumentation’ which makes possible a collectively valid distinction between the ‘is’ and the ‘ought’ of some disputed particular moral issue. A comparison with a land litigation among Trobriands (Papua New Guinea) shows that the ‘logic of argumentation’ and the corresponding basic moral beliefs of Trobriands very much resemble the ‘logic of argumentation’ and moral rationality standards of (German) adolescents. (shrink)