This chapter is divided into five main sections: (1) a historical presentation and critical discussion of possible demarcation criteria between religious beliefs and science; (2) a critical discussion—in the field of education—of different taxonomies of positioning between science and religious beliefs (e.g., Yasri et al., 2013), (3) the presentation of a typology (Wolfs et al., 2021) distinguishing several secularized or non-secularized conceptions of science; (4) a brief overview of an international survey conducted in 18 countries to determine the extent to which senior high school students have a secularized or non-secularized conception on science, (5) a discussion of the didactic implications of these theoretical considerations and empirical results.