On a Theory of Cultural Group Selection. A Case Study of the Spread of Christianity in the Roman Empire

The goal of the paper is to evaluate a theory of cultural group selection, i.e. a  theory which purports to explain an evolution of cultural artefacts (e.g. religious beliefs or ethical ideas). In order to realize this aim, the concept of the explanatory power of a theory T is introduced in the paper. The concept allows for two parameters: the extent of a theory, i.e., a quantity of phenomena explained by this theory, and a quantity of alternative theories explaining in an at least prima facie plausible way phenomena that belong to the extent of theory T. The argumentation pursued in the paper is supposed to justify three main claims: that the extent of the theory cultural group selection is not universal (because it does not embrace, e.g., scientific ideas); that there are other theories which explain plausibly the evolution of cultural artefacts; and that the two first claims do not undermine the value of the theory of cultural group selection. The last part of the paper is connected with the third
claim: it is a case-study of the spread of Christianity in the Roman Empire; the study is based on the theory of cultural group selection and is to serve as an exemplification of a more general thesis which says that it is the competition of religious beliefs that can be especially fruitfully modeled by means of the theory of cultural group selection.