 In 1917 a special professorship in ascetical and mystical theology was created for him at the "Angelicum", the first of its kind anywhere in the world.He is best known for his spiritual theology.His "magnum opus" in the field is "The Three Ages of the Interior Life" (Les Trois Ages de la Vie Interieure), in which he propounded the thesis that infused contemplation and the resulting mystical life are in the normal way of holiness of Christian perfection.