The present paper studies how the Belgian mathematician Paul Mansion became interested in probability theory. The Belgian mathematical environment, in which probability was present more than in many other countries at the same time appears to have been favorable but also the fact that Mansion, a declared and militant Catholic, found in probability a source of reflection about determinism and randomness in the context of the "modernist crisis" in the Church. Mansion's activity developed on the background of the scholar wars and the foundation of Catholic institutions such as the Institute for philosophy in Louvain, of the consolidation of mathematical education in Belgium as well as of a new interest for probabilistic results in science. We expose how these aspects intersected at the turn of the 20 th century.