The present document is presented as a sort of "open booklet" on the important issue of secularism in France, based essentially on studies, reports and texts that already exist on the subject, as well as on renowned authors who are specialists in the issue. Since its promulgation on December 9, 1905, the law on secularism has been part of the cultural, moral and political heritage of our country since at least the Third Republic. It is the result of long years of gestation and reflections, surrounded by its procession of often violent conflicts, but with in the background, however, a single goal turned towards the search for the "common good", in "respect, tolerance and dialogue". It is in this sense that this law can be apprehended, without evading its initial vocation; with the constant concern of "justice and equity"; more than one hundred years later, at the dawn of a new century that promises to be tumultuous; and by taking into account, of course, the sociological evolutions of our country.