Sources of Catholic moral theology include both the Old Testament and the New Testament, and philosophical ethics such as natural law that are seen as compatible with Catholic doctrine. Moral theology was mostly undifferentiated from theology in general during the patristic era, and is found in the homilies, letters and commentaries on Scripture of the early Church fathers. During the Middle Ages, moral theology developed in precision and scope through scholasticism. Much of the Catholic Church's current moral theology, especially regarding natural law, is based in the Summa Theologica by St. Thomas Aquinas, which is regarded as one of the best treatises of Catholic moral theology. Contemporary Catholic moral theology is developed by acts of the Magisterium, by the Pope, other bishops, and by the works of lay Catholic moral theologians, which include magisterial teachings, as well as theological opinions. Examples of Catholic moral theologians include St. Alphonsus Liguori, Germain Grisez and John Finnis. Moral theology tends to be advanced most authoritatively through official statements of doctrine, such as papal encyclicals, which are based on the dogmatic pronouncements of Ecumenical Councils, Sacred Scriptures, and Sacred Tradition. In addition, moral theologians publish their own works and write in a variety of journals devoted in whole, or in part to moral theology. These scholarly journals are helpful in making the theology of the Church more clear and accessible to others, and serve as a forum in which scholarly discussion of understanding and application of issues occurs. However, these journals per se do not add or remove anything from Catholic teaching. The curriculum for formation of priests commonly includes required and elective courses in Catholic moral theology.
Approaches to Catholic moral theology
In a deontological approach, morality takes the form of a studying of "how one is to act" in relation to the laws established by the faith.
In a teleological approach, "how one is to act" is related to the ultimate end which is again established by the faith.
In a dialogical approach, morality follows the pattern of faith directly, the "how one is to act" is related to an encounter with God through faith. Moral living is response to the Logos or Word of God. "Faith in the Logos...understands moral values as responsibility, as a response to the Word, and thus gives them their intelligibility as well as their essential orientation."
