In May 1956 Pope Pius XII issued his famous encyclical, Haurietis Aquas, on the subject of devotion to the Sacred Heart of Jesus. This volume contains an introduction and commentary, followed by the English text of the encyclical. The introduction and commentary serve to locate the encyclical historically and theologically with regard to previous pronouncements and devotional developments, to make clear the logical order employed by the Pope, to give fuller contexts for the scriptural references made in the text, to stress the precise value and significance of the doctrine it teaches, to paraphrase the separate paragraphs and to supply useful collateral information. The author establishes that the encyclical ""contains...a complete Christological treatise, and all the fundamental principles of the spiritual life."" No Catholic should have to be urged to read the encyclical itself, wherein the true nature of devotion to the Sacred Heart as rooted in Scripture, tradition and the liturgy is set in opposition to various modern objections raised against it and to the sentimental abuses of the devotion as well, that serve only to debase the devotion and bring it into disrepute. The commentary is useful for classroom and study-club purposes. It can profitably be used by the general reader who for one reason or another feels he needs a guide to the reading of the official document itself. The commentary aims more at clarifying, expanding and emphasizing than at deepening and developing the theological implications of the papal text.