He was born in Villeneuve-sur-Fère (Aisne), into a family of farmers and government officials. His father, Louis-Prosper, dealt in mortgages and bank transactions. His mother, the former Louise Cerveaux, came from a Champagne family of Catholic farmers and priests. Having spent his first years in Champagne, he studied at the "lycée" of Bar-le-Duc and at the Lycée Louis-le-Grand in 1881, when his parents moved to Paris. An unbeliever in his teenage years, he experienced a sudden conversion at the age of eighteen on Christmas Day 1886 while listening to a choir sing Vespers in the cathedral of Notre Dame de Paris: "In an instant, my heart was touched, and I believed." He would remain an active Catholic for the rest of his life. He studied at the Paris Institute of Political Studies (better known as Sciences Po).