Conversion by the Numbers: Benefits and Pitfalls of Quantitative Modelling in the Study of Early Christian Growth

Proponents and critics of numerically modelling early Christian growth have missed many complexities of this approach. This study re‐examines quantitative modelling by conducting “thought experiments,” built from initial assumptions to population projections. First, an “apostolic mission” model assumes that Christianity grew via persuasive leaders; it projects a cubic growth curve. Second, a “values reproduction” model ties higher reproduction and conversion to certain Christian values; it projects an exponential curve. Next, a “social reaction” model links growth to interconfessional interactions; it projects a logistic curve. Such formal models reveal numerical parameters of conversion and the impact of various assumptions. Together, they illustrate the variability of early Christian population projections. They also showcase limitations of traditional quantitative modelling, which tends to oversimplify social conditions, to mischaracterise ancient religion, and to inspire teleological reasoning. Newer “network” models can overcome only some of these limitations. Used carefully, however, quantitative methods supplement familiar socio‐cultural approaches.