All Catholics should progress through three “conversions” in their spiritual life. Yet many do not and thus remain spiritually stunted all their lives. Fr. Garrigou-Lagrange, one of the greatest theologians of the twentieth century, explains the classic Catholic traditions on the spiritual life from Scripture, the Fathers, St. Thomas Aquinas, St. John of the Cross, and St. Catherine of Siena. He explains the purgative, illuminative, and unitive ways, and addresses Martin Luther’s errors in spirituality.