St. Alphonsus Liguori was named a doctor of the Church because of his significant contributions in moral theology. The subject of Conscience is the first treatise in his work Moral Theology (Theologia Moralis). The careful way in which St. Alphonsus outlines the steps to reach a moral decision within a system of principles guarantees the dignity of a personal conscience. Fr. Raphael Gallagher, CSsR, a moral theologian, has produced a faithful and pastoral translation of Leonard Gaudé's critical edition from its original ecclesiastical Latin. Fr. Raphael also provides commentaries on each chapter that place the work in context and make the 18th-century text relevant for today. This is an essential treatise for those who wish to understand St. Alphonsus' approach to moral theology.