Secularism is a difficult concept to pinpoint. Indeed, it has never been officially defined, even in the few countries where secularism figures as one of the founding principles of the constitution. If anything, the meanings attributed to secularism evolve according to historical contexts and political issues. This encourages the spread of multiple representations-all legitimate-of what secularism might be, in turn feeding the scientific debate. To researchers, the inherent polysemy of the term secularism evokes the dynamic nature of the social reality they seek to analyze. This text, aligned with this perspective, stresses the importance of sociographic research on secularism, including the study of its historical trajectories, philosophical foundations, legal underpinnings and the social debates it provokes and that prove essential for a comprehensive analysis of the topic.