How does the Church help us to lead a good, responsible life?
In the Church we are baptized. In the Church we receive the faith that the Church has preserved intact down through the centuries. In the Church we hear the living Word of God and learn how we must live if we want to please God. Through the sacraments that Jesus entrusted to his disciples, the Church builds us up, strengthens, and consoles us. In the Church there is the blazing fire of the saints, by which our hearts are kindled. In the Church the Holy Eucharist is celebrated, in which Christ's sacrifice and strength are renewed for us in such a way that, united with him, we become his Body and live by his strength. Despite all her human weaknesses, apart from the Church no one can be a Christian.
Why does the Church also make declarations about ethical questions and about matters of personal conduct?
Believing is a path. One learns how to stay on this path, in other words, how to act rightly and to lead a good life, only by following the instructions in the Gospel. The teaching authority (Magisterium) of the Church must remind people also about the demands of the natural moral law.
There are not two truths. What is humanly right cannot be wrong from the Christian perspective. And what is right according to Christianity cannot be humanly wrong. That is why the Church must teach comprehensively about moral issues. (YOUCAT questions 343-344)
Dig Deeper: CCC section (2030-2040) and other references here.
Part 3: Life in Christ (1691 - 2557)
Section 1: Man's Vocation — Life in the Spirit (1699 - 2051)
Chapter 3: God's Salvation: Law and Grace (1949 - 2051)
Article 3: The Church, Mother and Teacher (2030 - 2051)
It is in the Church, in communion with all the baptized, that the Christian fulfills his vocation. From the Church he receives the Word of God containing the teachings of "the law of Christ."72 From the Church he receives the grace of the sacraments that sustains him on the "way." From the Church he learns the example of holiness and recognizes its model and source in the all-holy Virgin Mary; he discerns it in the authentic witness of those who live it; he discovers it in the spiritual tradition and long history of the saints who have gone before him and whom the liturgy celebrates in the rhythms of the sanctoral cycle.
72.
The moral life is spiritual worship. We "present [our] bodies as a living sacrifice, holy and acceptable to God,"73 within the Body of Christ that we form and in communion with the offering of his Eucharist. In the liturgy and the celebration of the sacraments, prayer and teaching are conjoined with the grace of Christ to enlighten and nourish Christian activity. As does the whole of the Christian life, the moral life finds its source and summit in the Eucharistic sacrifice.
73.
I. MORAL LIFE AND THE MAGISTERIUM OF THE CHURCH ⇡
The Church, the "pillar and bulwark of the truth," "has received this solemn command of Christ from the apostles to announce the saving truth."74 "To the Church belongs the right always and everywhere to announce moral principles, including those pertaining to the social order, and to make judgments on any human affairs to the extent that they are required by the fundamental rights of the human person or the salvation of souls."75
74.
1 Tim 3:15; LG 17.
75.
CIC, can. 747 § 2.
The Magisterium of the Pastors of the Church in moral matters is ordinarily exercised in catechesis and preaching, with the help of the works of theologians and spiritual authors. Thus from generation to generation, under the aegis and vigilance of the pastors, the "deposit" of Christian moral teaching has been handed on, a deposit composed of a characteristic body of rules, commandments, and virtues proceeding from faith in Christ and animated by charity. Alongside the Creed and the Our Father, the basis for this catechesis has traditionally been the Decalogue which sets out the principles of moral life valid for all men.
The Roman Pontiff and the bishops are "authentic teachers, that is, teachers endowed with the authority of Christ, who preach the faith to the people entrusted to them, the faith to be believed and put into practice."76 The ordinary and universal Magisterium of the Pope and the bishops in communion with him teach the faithful the truth to believe, the charity to practice, the beatitude to hope for.
76.
LG 25.
The supreme degree of participation in the authority of Christ is ensured by the charism of infallibility. This infallibility extends as far as does the deposit of divine Revelation; it also extends to all those elements of doctrine, including morals, without which the saving truths of the faith cannot be preserved, explained, or observed.77
77.
Cf. LG 25; CDF, declaration, Mysterium Ecclesiae 3.
The authority of the Magisterium extends also to the specific precepts of the natural law, because their observance, demanded by the Creator, is necessary for salvation. In recalling the prescriptions of the natural law, the Magisterium of the Church exercises an essential part of its prophetic office of proclaiming to men what they truly are and reminding them of what they should be before God.78
78.
Cf. DH 14.
The law of God entrusted to the Church is taught to the faithful as the way of life and truth. The faithful therefore have the right to be instructed in the divine saving precepts that purify judgment and, with grace, heal wounded human reason.79 They have the duty of observing the constitutions and decrees conveyed by the legitimate authority of the Church. Even if they concern disciplinary matters, these determinations call for docility in charity.
79.
Cf. CIC, can. 213.
In the work of teaching and applying Christian morality, the Church needs the dedication of pastors, the knowledge of theologians, and the contribution of all Christians and men of good will. Faith and the practice of the Gospel provide each person with an experience of life "in Christ," who enlightens him and makes him able to evaluate the divine and human realities according to the Spirit of God.80 Thus the Holy Spirit can use the humblest to enlighten the learned and those in the highest positions.
80.
Cf. 1 Cor 2:10-15.
Ministries should be exercised in a spirit of fraternal service and dedication to the Church, in the name of the Lord.81 At the same time the conscience of each person should avoid confining itself to individualistic considerations in its moral judgments of the person's own acts. As far as possible conscience should take account of the good of all, as expressed in the moral law, natural and revealed, and consequently in the law of the Church and in the authoritative teaching of the Magisterium on moral questions. Personal conscience and reason should not be set in opposition to the moral law or the Magisterium of the Church.
81.
Cf. Rom 12:8,11.
Thus a true filial spirit toward the Church can develop among Christians. It is the normal flowering of the baptismal grace which has begotten us in the womb of the Church and made us members of the Body of Christ. In her motherly care, the Church grants us the mercy of God which prevails over all our sins and is especially at work in the sacrament of reconciliation. With a mother's foresight, she also lavishes on us day after day in her liturgy the nourishment of the Word and Eucharist of the Lord.