Alphonse-Joseph-Auguste Gratry (18051872) was born in Lille, northern France, of irreligious parents and lived during a time of endless revolution. As a young man, he underwent a powerful conversion in which he experienced a mystical vision of a world based on truth and justice. This determined the course of his future life. A classically educated scholar, he studied engineering at the outstanding Ecole Polytechnique, completed a doctorate on the scientific method in Strasbourg (1840), was ordained a priest, and later obtained a doctorate in letters and a licentiate in theology. Moved by the events of 1848, he published his first book in the form of a social catechism on the necessity for a systematic response to the needs of society. In a parallel initiative to that of Blessed John Henry Cardinal Newman in England, he relaunched the Congregation of the Oratory in Paris (1852) with Pierre Petetot to raise intellectual standards among the clergy after the Revolution. A charismatic individual, well known as a distinguished logician, theologian, social thinker, and outstanding educator, preacher, and spiritual director, his major philosophical works appeared in the 1850s. The French Academy recognized his genius with election to the chair held by Voltaire a century earlier. Gratry fell into disfavor for his adhesion to the International Peace League on the eve of Frances war with Germany, and for his stand in regard to papal infallibility before Vatican I (a position largely vindicated in Vatican II), but he accepted the much narrower declaration once it was made. His most famous work, Les Sources, widely published until World War II, offers a plan of studies and a plan of life which reflect Gratrys philosophy of the person. The Christian Democratic Parties, the French lay movement Le Sillon, the Young Christian Workers (YCW), and the writings of Peter Maurin, mentor to todays Catholic Worker movement, witness to his foundational and comprehensive influence. For the first time in English, we have Julian Mariass (19142005) clear and accessible study (5th ed.) on the core of Alphonse Gratrys philosophy. Although he lived more than a century ago (18051872), Gratry addresses issues of concern today: the ontology of the human person with its body/soul unity; the intrinsic relationship of individuals to society and nature; and the problem of God. Recognized as a master in his lifetime with the rapid reprinting of his Logic, The Knowledge of God, and The Knowledge of the Soul, Gratry was relegated to near oblivion less than seventy years later with the rejection of metaphysics and the rise of Positivism. Marias reclaims Gratrys place in the history of philosophy and thoroughly explains Gratrys original logic written from the point of view of the juncture of philosophy and the human spirit. He shows how Gratrys theory of induction, in Platos original and foundational sense (Rep. VI), forms the heart of his metaphysics of knowledgethe science of transcendence by which the mind intellectually apprehends all reality: corporeal, psychic, and divine. Gratry thus establishes a complete ontology of the human personrational, free, and endowed with a three-fold sense: external, intimate (sens intime), and divinedependent on unlimited being or God. Gratrys original logic and metaphysics stands on its own philosophical basis, but in Chapter 6, Five Interior Adventures, Marias includes a parallel, existential foundation drawn from Gratrys private journal. This reveals how the young atheist underwent a series of near mystical experiences which gave him an inescapable awareness of God and confronted him with the moral choice for or against this reality. In this extraordinarily lucid study, we now have access to the complete thought of Gratry, giving scholar and student, as Marias observes, a seemingly providential body of work needed in our time.