As he left Rennes, to begin a new stage in his life, Louis Marie acted out a little drama which was symbolic of the life-style he had now determined to pursue. His family had offered him a horse to ride to Paris, but this he refused; his mother provided him with a new suit of clothes, and his father presented him with 10 écus to cover the expenses of his journey. Some of his family accompanied him as far as Cesson, where the road to Paris crossed the River Villaine, and there said their good-byes to him. Crossing over the bridge, Louis Marie took the first opportunity offered to him to give away his 10 écus, and then to exchange his new clothes for those of a beggar, and continued on his way, determined from then on to rely solely on Providence for his needs, and to live close to the poor.
When he arrived in Paris, it was to find that his benefactor had not provided enough money for him to enter even the "Little Saint-Sulpice", as it was called - a separate college linked with the main seminary, but provided especially for the poorer students. So he lodged instead in a succession of boarding houses run by some of the Sulpician priests, where the diet was poor and the accomodation sparse, in the meantime attending the Sorbonne University for lectures in theology. Perhaps with rash over-enthusiasm, he added his own penances to the rigours of this life, with the result that, after less than two years, he became very ill and had to be hospitalized in the Hotel-Dieu. It was almost a miracle that he survived both his illness and the blood-lettings administered as part of his hospital treatment; and perhaps even more of a miracle that, on his release from hospital, he found himself with a place reserved at the Little Saint-Sulpice, which he entered in July 1695.
Saint-Sulpice had been founded by Jean-Jacques Olier, one of the leading exponents of what came to be known as the "French School of Spirituality". With its emphasis on the mystery of the Incarnation, and on the place of Mary in God's Plan of Salvation, it was an ideal place for Louis Marie to develop the themes of his personal spirituality. Yet, other aspects of Sulpician spirituality do not seem to have attracted him so much: the tendency to place the clergy on a pedestal, to the point where there was a danger of their becoming "settled", not to say smug. His time at Saint-Sulpice, however, gave him the opportunity to study most of the available works on spirituality and, in particular, on Mary's place in the Christian life, especially when he was appointed librarian, nor did he waste the opportunity. He also had time to develop catechetical skills, especially among the deprived youth of Saint-Sulpice parish.
The time arrived for him to be ordained a priest in June 1700, and a few days later he said his first Mass at the altar of the Blessed Virgin in the church of Saint-Sulpice. He remained for a few more months in Paris, before setting out on his priestly ministry.