This article critically explores the explanations of religious dynamics in Argentina based on Secularization Theory (TdS). Most scholarship uses political-institutional relations as an independent variable; therefore, TdS focuses on what takes place within the leadership of the institution and intermediate organizations. This research collects data directly from a century of baptism records in the city of Córdoba (Argentina) and compares it with the city’s birth rate. This analysis shows that the use of political-institutional variables fails to adequately explain religious dynamics, as measured in baptisms. The proposed hypothesis is that religious transformations are better understood when demographic variables are applied.