Although not well-known in the English-speaking world, Fr. Ambroise Gardeil, OP (1859-1931) was a Dominican of significant influence in French Catholic thought at the turn of the 20th century. Conservative theologians like Frs. Reginald Garrigou-Lagrange, OP, Michel Labourdette, OP, Jean-Hervé Nicolas, OP and many others hailed him as a careful expositor of the supernaturality of faith, a defender of the theological nature of rational apologetics, and a spiritual master. In his controversial Le Saulchoir: Une école de théologie, Fr. Marie-Dominique Chenu, OP praised Fr. Gardeil as an important Dominican initiator of reforms in historical theology, presenting the latter as a kind of precursor to one of the streams of what is now referred to historically as the “Nouvelle Théologie.” And one cannot read the words of Fr. Gardeil’s contemporary Fr. Antoine Lemonnyer, OP, without hearing echoes and re-echoes of common cause regarding our lofty spiritual vocation, resounding within the halls of the Saulchoir. With such a broad appeal, it is no surprise that in private correspondence, a young Yves Simon, writing to Jacques Maritain, referred to Fr. Gardeil as “The Great Gardeil.” The True Christian Life provides a thorough and stirring introduction to Fr. Gardeil’s work in spiritual theology. The volume was originally published posthumously through the collaboration of Fr. Gardeil’s nephew, Fr. Henri-Dominique Gardeil, OP and Jacques Maritain. Fr. Ambroise, prior to beginning work on his masterpiece on spiritual experience, La Structure de l'âme et l'expérience mystique, drafted nearly eight-hundred pages that would have set forth a full presentation of moral-ascetical theology. While drafting this massive work, his reflection on the soul’s receptive capacity for grace led him to the two-volume study, La Structure, and he never was able to finish his original designs for a comprehensive study of the Christian moral-spiritual life. Soon after his death, his nephew gathered several essays from the Revue thomiste and Revue de Jeunes, along with a complete-but-unpublished study on prayer. Drafting a lengthy introduction on the basis of Fr. Ambroise’s unpublished notes, Fr. Henri-Dominique assembled a volume of moral / spiritual theology that sets out the principles of many important themes: divinization through grace, Christian prudence /conscience, the virtue of religion, devotion, and prayer. In his In memoriam written after the passing of Fr. Gardeil, Fr. Reginald Garrigou-Lagrange emphasized Fr. Gardeil’s ability to meditate on a given topic’s central principles, like someone who sees the highest peaks that give structure to the entire mountain range of theology. In this volume, the reader will find a clear and rhetorically striking presentation of the central mysteries of the spiritual life, presented with stirring and beautiful rhetoric by a theological master from the Thomist tradition.