Today’s Catechism sections discuss the moral life and missionary witness. Supporting material comes from the Decree on the Apostolate of the Laity, “Apostolicam Actuositatem”.
III. Moral Life and Missionary Witness
2044 The fidelity of the baptized is a primordial condition for the proclamation of the Gospel and for the Church's mission in the world. In order that the message of salvation can show the power of its truth and radiance before men, it must be authenticated by the witness of the life of Christians. "The witness of a Christian life and good works done in a supernatural spirit have great power to draw men to the faith and to God."88
2045 Because they are members of the Body whose Head is Christ,89 Christians contribute to building up the Church by the constancy of their convictions and their moral lives. The Church increases, grows, and develops through the holiness of her faithful, until "we all attain to the unity of the faith and of the knowledge of the Son of God, to mature manhood, to the measure of the stature of the fullness of Christ."90
2046 By living with the mind of Christ, Christians hasten the coming of the Reign of God, "a kingdom of justice, love, and peace."91 They do not, for all that, abandon their earthly tasks; faithful to their master, they fulfill them with uprightness, patience, and love.
2049 The Magisterium of the Pastors of the Church in moral matters is ordinarily exercised in catechesis and preaching, on the basis of the Decalogue which states the principles of moral life valid for every man.
2050 The Roman Pontiff and the bishops, as authentic teachers, preach to the People of God the faith which is to be believed and applied in moral life. It is also encumbent on them to pronounce on moral questions that fall within the natural law and reason.
2051 The infallibility of the Magisterium of the Pastors extends to all the elements of doctrine, including moral doctrine, without which the saving truths of the faith cannot be preserved, expounded, or observed.
The Ten Commandments
Exodus 20 2-17
I am the LORD your God, who brought you out of the land of Egypt, out of the house of bondage.
You shall have no other gods before me. You shall not make for yourself a graven image, or any likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth; you shall not bow down to them or serve them; for I the LORD your God am a jealous God, visiting the iniquity of the fathers upon the children to the third and the fourth generation of those who hate me, but showing steadfast love to thousands of those who love me and keep my commandments.
You shall not take the name of the LORD your God in vain; for the LORD will not hold him guiltless who takes his name in vain.
Remember the sabbath day, to keep it holy. Six days you shall labor, and do all your work; but the seventh day is a sabbath to the LORD your God; in it you shall not do any work, you, or your son, or your daughter, your manservant or your maidservant or your cattle, or the sojourner who is within your gates; for in six days the LORD made heaven and earth, the sea, and all that is in them, and rested the seventh day; therefore the Lord blessed the sabbath day and hallowed it.
Honor your father and your mother, that your days may be long in the land which the LORD your God gives you.
You shall not kill.
You shall not commit adultery.
You shall not steal.
You shall not bear false witness against your neighbor.
You shall not covet your neighbor's house; you shall not covet your neighbor's wife, or his manservant or his maidservant or his ox, or his ass, or anything that is your neighbor's.
I am the LORD your God, who brought you out of the land of Egypt out of the house of bondage. You shall have no other gods before me . . .
You shall not take the name of the LORD your God in vain . . .
Observe the sabbath day, to keep it holy. . .
Honor your father and your mother . . .
You shall not kill.
Neither shall you commit adultery.
Neither shall you steal.
Neither shall you bear false witness against your neighbor.
Neither shall you covet your neighbor's wife .
You shall not desire . . . anything that is your neighbor's.
A Traditional Catechetical Formula
1. I am the LORD your God: you shall not have strange Gods before me.
2. You shall not take the name of the LORD your God in vain.
3. Remember to keep holy the LORD'S Day.
4. Honor your father and your mother.
5. You shall not kill.
6. You shall not commit adultery.
7. You shall not steal.
8. You shall not bear false witness against your neighbor.
9. You shall not covet your neighbor's wife.
10. You shall not covet your neighbor's goods.
The Decree on the Apostolate of the Laity, “Apostolicam Actuositatem” discusses the mission of the Church and the missionary witness it provides.
6. The mission of the Church pertains to the salvation of men, which is to be achieved by belief in Christ and by His grace. The apostolate of the Church and of all its members is primarily designed to manifest Christ's message by words and deeds and to communicate His grace to the world. This is done mainly through the ministry of the Word and the sacraments, entrusted in a special way to the clergy, wherein the laity also have their very important roles to fulfill if they are to be "fellow workers for the truth" (3 John 8). It is especially on this level that the apostolate of the laity and the pastoral ministry are mutually complementary.
There are innumerable opportunities open to the laity for the exercise of their apostolate of evangelization and sanctification. The very testimony of their Christian life and good works done in a supernatural spirit have the power to draw men to belief and to God; for the Lord says, "Even so let your light shine before men in order that they may see your good works and give glory to your Father who is in heaven" (Matt. 5:16).
However, an apostolate of this kind does not consist only in the witness of one's way of life; a true apostle looks for opportunities to announce Christ by words addressed either to non-believers with a view to leading them to faith, or to the faithful with a view to instructing, strengthening, and encouraging them to a more fervent life. "For the charity of Christ impels us" (2 Cor. 5:14). The words of the Apostle should echo in all hearts, "Woe to me if I do not preach the Gospel" (1 Cor. 9:16).(1)
Since, in our own times, new problems are arising and very serious errors are circulating which tend to undermine the foundations of religion, the moral order, and human society itself, this sacred synod earnestly exhorts laymen-each according to his own gifts of intelligence and learning-to be more diligent in doing what they can to explain, defend, and properly apply Christian principles to the problems of our era in accordance with the mind of the Church.
88 AA 6 # 2.
89 Cf. ⇒ Eph 1:22.
90 ⇒ Eph 4:13; cf. LG 39.
91 Roman Missal, Preface of Christ the King.