The book deals with a new scientific approach developed under the Title of “General Subject Didactics”. This concept can be defined as the theory of Subject didactics. It observes and reflects on how the individual Subject didactics explore Subject-specific teaching and learning, both by top-down reflections and by bottom-up comparisons. The empirical basis derives from a comprehensive study in Germany where 17 Subject didactics were compared on the basis of six impulses, e. g. reference sciences of Subject didactics, sources and selection of Subject content or research formats applied. This allows to gain insights into the commonalities of all related disciplines and helps to identify differences among them.