In the formation of their consciences, the Christian faithful ought carefully to attend to the sacred and certain doctrine of the Church (cf. Pius XII, radio message, March 23, 1952). For the Church is, by the will of Christ, the teacher of the truth. It is her duty to give utterance to, and authoritatively to teach, that truth which is Christ Himself, and also to declare and confirm by her authority those principles of the moral order which have their origins in human nature itself (Vatican Council II, Declaration Dignitatis humanae, no. 14, December 7, 1965)

As for you, Venerable Brethren, carry on diligently with the work of the Saviour of men by emulating His gentleness and His strength. Minister to every misery; let no sorrow escape your pastoral solicitude; let no lament find you indifferent. But, on the other hand, preach fearlessly their duties to the powerful and to the lowly; it is your function to form the conscience of the people and of the public authorities. The social question will be much nearer a solution when all those concerned, less demanding as regards their respective rights, shall fulfill their duties more exactingly. (Pius X. Notre charge apostolique, no. 39, August 23, 1910)

Certainly the loving Mother is spotless in the Sacraments by which she gives birth to and nourishes her children; in the faith which she has always preserved inviolate; in her sacred laws imposed on all; in the evangelical counsels which she recommends; in those heavenly gifts and extraordinary grace through which with inexhaustible fecundity (cf. Vat. Council I, Sess. III, de fide Cath., cap 3), she generates hosts of martyrs, virgins and confessors. But it cannot be laid to her charge if some members fall, weak or wounded. In their name she prays to God daily: ‘Forgive us our trespasses;’ and with the brave heart of a mother she applies herself at once to the work of nursing them back to spiritual health. (Pius XII. Encyclical Mystici Corporis Christi, no. 66, June 29, 1943)

At a time when in the sphere of morality there is a disturbing spread of relativism and subjectivism, the Church in America is called to proclaim with renewed vigor that conversion consists in commitment to the person of Jesus Christ, with all the theological and moral implications taught by the Magisterium of the Church. There is a need to recognize ‘the role played by theologians, catechists and religion teachers who, by setting forth the Church’s teaching in fidelity to the Magisterium, cooperate directly in the correct formation of the consciences of the faithful’ (Propositio 68). (John Paul II. Apostolic Exhortation Ecclesia in America, January 22, 1999)

It is necessary to turn again to some fundamental concepts of Catholic doctrine in order to duly understand that the conscience can and should be educated. The divine Savior has brought to man, ignorant and weak, his truth and grace: truth to indicate the path that leads to his end; grace to give him the strength to be able to reach it. […] But, where may the educator and the educated find, concretely with facility and certainty, the moral Christian law? In the law of the Creator, engraved on the heart of each one, (cf Rom 2: 14-16), and in revelation; that is to say, in the ensemble of truths and precepts taught by the divine Master. Both, the law engraved in the heart, which is the natural law, as well as the truths and precepts of supernatural revelation, were left by Jesus the Redeemer, as the moral treasure of humanity, in the hands of his Church, so that she may preach them to all peoples, explaining and transmitting them integrally and free of all contamination and error from generation to generation. […] Conscious, therefore, of the right and the obligation of the Holy Apostolic See to intervene, when it be necessary, authoritatively in moral questions, We in the address of October 29 last year, proposed to enlighten the consciences in that which refers to the problems of conjugal life. With the same authority we declare today to educators and to the youth: the divine commandment of the purity of soul and body is also necessary without diminishment for the youth of today. They in the same way, have the moral obligation – and with the help of grace – the possibility of keeping themselves pure. eposciences, (Pius XII. Radio message for the celebration of ‘Family Day’, March 23, 1952)

For here Our concern is with the doctrine of the Catholic and Apostolic Church. She is the Mother and Teacher of all nations. Her light illumines, enkindles and enflames. No age but hears her warning voice, vibrant with heavenly wisdom. She is ever powerful to offer suitable, effective remedies for the increasing needs of men, and the sorrows and anxieties of this present life. (John XXIII. Encyclical Mater et magistra, no. 262, May 15, 1961)

She is ‘the pillar and ground of the truth’ (Cf. 1Tim. 3:15). To her was entrusted by her holy Founder the twofold task of giving life to her children and of teaching them and guiding them—both as individuals and as nations—with maternal care. Great is their dignity, a dignity which she has always guarded most zealously and held in the highest esteem. (John XXIII. Encyclical Mater et magistra, no. 262, May 15, 1961)

In fact, it is the mission of the Church to form consciences and to offer criteria in such delicate matters that have a great influence on behaviour and on the moral principles of people, especially on children and youth. (John Paul II. Address to the  Ambassador of Costa Rica to the Holy See)

Christians have a great help for the formation of conscience in the Church and her Magisterium. As the Council affirms: ‘In forming their consciences the Christian faithful must give careful attention to the sacred and certain teaching of the Church. For the Catholic Church is by the will of Christ the teacher of truth. Her charge is to announce and teach authentically that truth which is Christ, and at the same time with her authority to declare and confirm the principles of the moral order which derive from human nature itself’ (Dignitatis Humanae, 14). (John Paul II. Encyclical Veritatis splendor, no. 64, August 6, 1993)

The Church’s fundamental function in every age and particularly in ours is to direct man’s gaze, to point the awareness and experience of the whole of humanity towards the mystery of God, to help all men to be familiar with the profundity of the Redemption taking place in Christ Jesus. At the same time man’s deepest sphere is involved – we mean the sphere of human hearts, consciences and events. (John Paul II. Encyclical Redemptor hominis, no. 10, March 4, 1979)

Yet one of the tasks of the Church in Africa consists in forming upright consciences receptive to the demands of justice, so as to produce men and women willing and able to build this just social order by their responsible conduct. (Benedict XVI. Apostolic Exhortation Africae munus, no. 22, November 19, 2011)

Sacramental Reconciliation re-establishes friendship with God the Father and with all his sons in his family which is the Church, which, in turn, is rejuvenated and edified in all of its dimensions: universal, diocesan, parochial (cf Council of Trent, sess. Vl, de iustificatione c. 14; sess. XIV, de poenitentia c. 1 2, 5-7, can. 10; sess. XXIII, de ordine c. 1; Vatican Council II, Presbyterorum Ordinis 2, 5). In spite of the reality of a loss of the sense of sin, greatly extended in the culture of our times, the priest must practice, with joy and dedication, the ministry of the formation of consciences, pardon and peace. (Congregation for the Clergy, Directory on the Ministry and Life of Priests, no. 51, March 31, 1994)

Since the Magisterium of the Church has been instituted by Christ the Lord to enlighten the conscience, appealing to this conscience precisely in order to contest the truth of all that the Magisterium teaches comports a rejection of the Catholic concept of the Magisterium and of moral conscience. To speak of the intangible dignity of the conscience without posterior specifications, brings on the risk of grave errors. (John Paul II. Address to the participants in the Second International Congress on Moral Theology, November 12, 1988)

Where, then, shall I begin? With authority, or with reasoning? In the order of nature, when we learn anything, authority precedes reasoning. For a reason may seem weak, when, after it is given, it requires authority to confirm it. But because the minds of men are obscured by familiarity with darkness, which covers them in the night of sins and evil habits, and cannot perceive in a way suitable to the clearness and purity of reason, there is most wholesome provision for bringing the dazzled eye into the light of truth under the congenial shade of authority. (Saint Augustine. Of the Morals of the Catholic Church, Ch. 2, no. 3)

How does the Church nourish the moral life of a Christian?
The Church is the community in which the Christian receives the Word of God, the teachings of the ‘Law of Christ’ (Gal 6:2), and the grace of the sacraments. Christians are united to the Eucharistic sacrifice of Christ in such a way that their moral life is an act of spiritual worship; and they learn the example of holiness from the Virgin Mary and the lives of the Saints.
Why does the Magisterium of the Church act in the field of morality?
It is the duty of the Magisterium of the Church to preach the faith that is to be believed and put into practice in life. This duty extends even to the specific precepts of the natural law because their observance is necessary for salvation. (Compendium of the Catholic Church. no. 429-430)

How is a moral conscience formed to be upright and truthful?
An upright and true moral conscience is formed by education and by assimilating the Word of God and the teaching of the Church. It is supported by the gifts of the Holy Spirit and helped by the advice of wise people. Prayer and an examination of conscience can also greatly assist one’s moral formation.
Can a moral conscience make erroneous judgments?
A person must always obey the certain judgment of his own conscience but he could make erroneous judgments for reasons that may not always exempt him from personal guilt. However, an evil act committed through involuntary ignorance is not imputable to the person, even though the act remains objectively evil. One must therefore work to correct the errors of moral conscience. (Compendium of the Catholic Church. no. 374 and 376)

In the formation of conscience the Word of God is the light for our path (Ps 119:105), we must assimilate it in faith and prayer and put it into practice. We must also examine our conscience before the Lord’s Cross. We are assisted by the gifts of the Holy Spirit, aided by the witness or advice of others and guided by the authoritative teaching of the Church (cf DzH 14). (Catechism of the Catholic Church, no. 1785)

Ministries should be exercised in a spirit of fraternal service and dedication to the Church, in the name of the Lord (Rom 12:8,11). 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. (Catechism of the Catholic Church, no. 2039)