Secularisation is ambiguous : it tends to both restrict the religious to its sphere, and to promote the diffusion of more or less secularised religious concepts into other areas. Thus, the contestation of Catholicism’s hold on French society in the first half of the 19th century not only led to the promotion of the division between State and Church, but also to the development of alternative religions based on extra-religious concepts in order to give coherence and meaning to the post-revolutionary world. We have contextualised these attempts according to the three fundamental demands of modern politics : that for liberalism, that for democracy, and that for conservatism. The failure of these religions of the future, those resulting from Saint-Simonianism and those issued from spiritualist approaches alike, is no reason not to give them their place in a history of secularisation, but rather explains the tensions within the French movement for laicism.