This essay outlines reasons why research in mathematics education requires didactical content analysis, understood as the rational evaluation of the educational suitability of different mathematical approaches towards a given curricular content on the basis of didactical background theories. It continues to argue that such work is currently being done outside of research and still being used in research. A reason for that is investigated via the example of a diminishing German manifestation of didactical content analysis. It becomes obvious that studies in didactical content analysis have become difficult or impossible to publish due to the lack of a methodology for the research field. Eventually, initial thoughts for such a methodology are presented.