I. God leads all things by His eternal law, often portrayed as Lady Wisdom in the Bible. See Ps. 19:7-10, 119; Prov. 3:13-25, 8:1-9:18; Sir, Sir. 1:1-18; Wis. 7:14-10:21; St. Thomas Aquinas points our, the eternal law is the primordial principal upon which all other governance is based. See Summa Theologica II-I q. 93 art. 1.

II. The conscience is the testimony to this moral law in each person, God's ambassador in the soul.

A. Each person has a conscience, a desire for truth and goodness. As St. Paul says, "When the Gentiles who do not have the law by nature observe the prescriptions of the law, they are a law unto themselves, even though they do not have the law. They show that the demands of the law are written in their heart." Rom. 1:14. Or as the Catechism says, AMoral conscience, present at the heart of the person, enjoins him at the appropriate moment to do good and to avoid evil. It also judges particular choices, approving those that are good and denouncing those that are evil. It bears witness to the authority of truth in reference to the supreme God to which the human person is drawn, and it welcomes the commandments. When he listens to his conscience, the prudent man can hear God speaking.@ Catechism 1777.

B. As a result, one should always abide by one's conscience, for it is our way of hearing God's commands. And this obligation is the firmest foundation for individual dignity and political rights. As the Vatican II Council's document on religious liberty says, this obligation to pursue the truth and adhere to it once known is the basis for religious and intellectual freedom. See Dignitatis Humanae 2. As Pope Benedict XVI wrote in Caritas in Veritate (2009) section 43, people today are often "concerned only with their rights, and they often have great difficulty in taking responsibility for their own and other people's integral development. Hence it is important to call for a renewed reflection on how rights presuppose duties, if they are not to become mere licence. Nowadays we are witnessing a grave inconsistency. On the one hand, appeals are made to alleged rights, arbitrary and non-essential in nature, accompanied by the demand that they be recognized and promoted by public structures, while, on the other hand, elementary and basic rights remain unacknowledged and are violated in much of the world"

D. Because the human conscience is fallible and limited, God reveals things to us about the moral law both by Scripture and the Church.

1. We are certainly called to develop our reason naturally by careful thinking, knowledge and consultations with other people. It is natural wisdom to understand that the development of a conscience is both essential and difficult.

III ASin is an offense against reason, truth, and right conscience; it is a failure in genuine love for God and neighbor caused by a perverse attachment to certain goods. It wounds the nature of man and injures human solidarity.@ Catechism 1849.

A. Most sins are venial, which means they weaken, but not destroy the friendship with God. However, some sins are mortal, which means that they will destroy our friendship with God if unrepented. Thus, St. John speaks of sins that are mortal and sins that are lesser. 1 John 5:16-17. And St. Paul lists some sins that prevent one from inheriting the kingdom of heaven. See Gal. 5:19-21. Such sins require repentance in order for the relationship with God to be restored; the ordinary means of such repentance in the Catholic Church is the sacrament of Reconciliation. See Catechism 1484.

- "The distinction between mortal and venial sin, already evident in Scripture, became part of the tradition of the Church. Mortal sin destroys charity in the heart of man by a grave violation of God=s law; it turns man away from God, who is his ultimate end and his beatitude. . . . Mortal sin is sin whose object is a grave matter and which is also committed with full knowledge and deliberate consent.@ Catechism 1854, 1855, 1857.

IV. Overcoming sin and achieving the holiness that we are all called to requires the grace of God and our own cooperation.