"Moral 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 Good 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." CCC 1777
Return of the Prodigal Son by Murillo
The Formation of a Moral Conscience
Unfortunately, conscience may be one of the most misunderstood things among Catholics in this modern age. Many Catholics, as well as others, have come to understand conscience itself as a source of moral law—meaning that one simply discerns the moral law by looking within himself. Thus, “I am following my conscience,” has come to mean little more than one is following his subjective inclinations, which are themselves often formed by the prevailing culture.
Conscience is, however, as understood and taught by the Church, a judgment of reason. It uses the objective standards of the moral law to judge the morality of acts in specific circumstances. Every man, therefore, has a duty to form his conscience by immersing himself in the teachings of Holy Scripture and the Holy Catholic Church. He must actually form his conscience by the objective moral truth, which he must then use to judge the morality of acts in the specific circumstances of life.
If you want to know what to think and do in the difficult circumstances of life, you must know what the Scriptures and the Church teach.
Works That Will Help You Form a Moral Conscience