From Pope St. John Paul II’s encyclical Veritatis Splendor (1993):
Within the unity of the Church, promoting and preserving the faith and the moral life is the task entrusted by Jesus to the Apostles (cf. Mt 28:19-20), a task which continues in the ministry of their successors. This is apparent from the living Tradition, whereby — as the Second Vatican Council teaches — “the Church, in her teaching, life and worship, perpetuates and hands on to every generation all that she is and all that she believes. This Tradition which comes from the Apostles, progresses in the Church under the assistance of the Holy Spirit”.39 In the Holy Spirit, the Church receives and hands down the Scripture as the witness to the “great things” which God has done in history (cf. Lk 1:49); she professes by the lips of her Fathers and Doctors the truth of the Word made flesh, puts his precepts and love into practice in the lives of her Saints and in the sacrifice of her Martyrs, and celebrates her hope in him in the Liturgy. By this same Tradition Christians receive “the living voice of the Gospel”,40 as the faithful expression of God’s wisdom and will.
Within Tradition, the authentic interpretation of the Lord’s law develops, with the help of the Holy Spirit. The same Spirit who is at the origin of the Revelation of Jesus’ commandments and teachings guarantees that they will be reverently preserved, faithfully expounded and correctly applied in different times and places. This constant “putting into practice” of the commandments is the sign and fruit of a deeper insight into Revelation and of an understanding in the light of faith of new historical and cultural situations. Nevertheless, it can only confirm the permanent validity of Revelation and follow in the line of the interpretation given to it by the great Tradition of the Church’s teaching and life, as witnessed by the teaching of the Fathers, the lives of the Saints, the Church’s Liturgy and the teaching of the Magisterium.
In particular, as the Council affirms, “the task of authentically interpreting the word of God, whether in its written form or in that of Tradition, has been entrusted only to those charged with the Church’s living Magisterium, whose authority is exercised in the name of Jesus Christ“.41 The Church, in her life and teaching, is thus revealed as “the pillar and bulwark of the truth” (1 Tim 3:15), including the truth regarding moral action. Indeed, “the Church has the right always and everywhere to proclaim moral principles, even in respect of the social order, and to make judgments about any human matter in so far as this is required by fundamental human rights or the salvation of souls”.42
Precisely on the questions frequently debated in moral theology today and with regard to which new tendencies and theories have developed, the Magisterium, in fidelity to Jesus Christ and in continuity with the Church’s tradition, senses more urgently the duty to offer its own discernment and teaching, in order to help man in his journey towards truth and freedom.
39 Dogmatic Constitution on Divine Revelation Dei Verbum, 8.
40 Cf. ibid.
41 Ibid., 10.
42 Code of Canon Law, Canon 747, 2.
— Veritatis Splendor 27