The Mystery of the Church represents the fi nal writings of Fr. Humbert Clerissac, O.P. In it, readers will fi nd much-needed spiritual nourishment, gaining insights into the beauty and glory of the Church's manifold mysteries. As Jacques Maritain writes in the Preface, Fr. Clerissac "asked of those who came to him to adhere fully to the mystery of the Church." Th is adherence, for Fr. Clerissac, depended on the dynamic union of faith and reason, nourished and guided by a living and tender charity. In his writings, preaching, and prayer, Fr. Clerissac strove to alleviate the spiritual affl ictions of modernity. Th e Mystery of the Church embodies his best eff orts and, although unfi nished, stands as a testament to his love of Christ who is the Way, the Truth, and the Life, and his desire to share that love and its light for the salvation of souls. Father Humbert Clerissac, O.P., was born in France in 1864. At the early age of sixteen, he discerned his vocation after reading Lacordaire's Life of Saint Dominic. During the thirty-four years of his Dominican life he showed a never-wavering ardor for the spirit of St. Dominic's life and mission. He had tremendous infl uence as a preacher and a spiritual director, and he worked tirelessly for conversions, giving retreats to religious men and women of his own and other Orders. Fr. Clerissac died in 1914, just before the outbreak of World War I.