This is the feast of that beautiful heart which is the abyss of all mysteries. By way of showing us that we are now living in the Age of Our Lady, this feast, first instituted in 1644, was given to the entire Catholic Church in 1944, by the late Pope Pius XII. The Immaculate Heart of Mary is of such spotless purity that it lives in contemplation and love of God alone. It is called by one of the saints, “the Furnace of Divine Love.” Mary’s is also the heart that is full of tenderness and love toward us, and is eager to give divine things to all those who greet it as Immaculate, and love it with all their hearts. Numberless saints have spread devotion to the Immaculate Heart of Mary. Two great priests deserve especially to be remembered in this crusade. They are Saint John Eudes (August 19) and Saint Louis Marie de Montfort (April 28). The authors of this book love to call themselves the Slaves of the Immaculate Heart of Mary. They would be slaves to no one else in this world. They consider being Slaves of the Immaculate Heart of Mary to be the greatest of all freedoms.