When Marc Sangnier died in Paris in 1950 and was buried in Notre Dame, the streets nearby filled with people who could not get into the cathedral. Before his death, the French government awarded Sangnier the Légion d'honneur, pinned to his lapel by François Mauriac, a former silloniste who became a noted man of letters. Le Sillon was a French political and religious movement founded by Sangnier, which existed from 1894 to 1910. It aimed to bring Catholicism into a greater conformity with French Republican and socialist ideals, in order to provide an alternative to Marxism and other anticlerical labour movements. This volume details the discovery of le Sillon as a lay movement in France that issued from the leadership of brilliant young students at the turn of the twentieth century. As they matured so did the aims of the movement, and they became an educational force that encouraged both the privileged and worker alike to join together in playing leadership roles in unions, then dominated by the anti-clerical left. Their activities brought them into conflict with the French hierarchy and the papacy itself and matured into an expression of Christian economic democracy that challenged Catholic hierarchical norms.