There is no filiation between the agnosticism of intellectual elites in previous centuries and today's decline of religious beliefs in the populace. The analysis is based on several international mass surveys concerning twenty European countries between 1980 and 2000. Religious beliefs are considered as observable social facts. Seven tables bring empirical evidence. The analysis of survey research are preceded by a review of the current sociological literature, particularly in France, on the "crisis of Catholicism", "dechristianisation", "paganisation", "apostasy", and of the papal encyclics and Episcopal declarations.