In this compact book; the famous Thomist; Fr. Garrigou-Lagrange; sets forth the classic Catholic traditions on the spiritual life as the full flowering of Sanctifying Grace in the soul. He explains the three stages of the spiritual life-the Purgative Way; the Illuminative Way; and the Unitive Way-showing the transitions or conversions from one period to another. How can one become a saint without knowing the way -- the pitfalls; common mistakes; and experience of Saints who have gone before. Friar Réginald Marie Garrigou-Lagrange OP., was a worldwide known Catholic Theologian and, among Thomists of the scholastic tradition, is generally thought to be the greatest Catholic Thomist of the Twentieth Century. He taught at the Pontifical University of St. Thomas Aquinas, commonly known as the Angelicum, in Rome from 1909 until 1960.Gontran-Marie Garrigou-Lagrange was born in Auch, Midi-Pyrénées, France, on February 21, 1877, into a solid Catholic family living in the south-west of France. In 1896, he began studies in medicine at the University of Bordeaux, but whilst there he read a book by the Catholic philosopher Ernest Hello which changed the direction of his life.Medical studies abandoned, Gontran-Marie entered the French Dominicans at the age of twenty, and received the Religious Name of Reginald, after Blessed Reginald of Orleans, a contemporary of St Dominic, to whom Our Lady appeared in a vision, curing him of a mortal sickness and gaving him a white scapular that thereupon became part of the Dominican habit. Friar Reginald had the good fortune to receive his initial training from Dominicans committed to implementing Pope Leo XIII's encyclical letter "Aeterni Patris", the document that insisted upon the unique place of St. Thomas Aquinas in Philosophy and Theology. It was by studying the Angelic Doctor that the young Reginald Garrigou-Lagrange nourished the conviction that had brought him to the cloister: the unchangeableness of revealed truth.