Catechism of the Catholic Church
1790 A human being must always obey the certain judgment of his conscience. If he were deliberately to act against it, he would condemn himself. Yet it can happen that moral conscience remains in ignorance and makes erroneous judgments about acts to be performed or already committed.
1791 This ignorance can often be imputed to personal responsibility. This is the case when a man "takes little trouble to find out what is true and good, or when conscience is by degrees almost blinded through the habit of committing sin." 59 In such cases, the person is culpable for the evil he commits.
1792 Ignorance of Christ and his Gospel, bad example given by others, enslavement to one's passions, assertion of a mistaken notion of autonomy of conscience, rejection of the Church's authority and her teaching, lack of conversion and of charity: these can be at the source of errors of judgment in moral conduct.
1793 If - on the contrary - the ignorance is invincible, or the moral subject is not responsible for his erroneous judgment, the evil committed by the person cannot be imputed to him. It remains no less an evil, a privation, a disorder. One must therefore work to correct the errors of moral conscience.
1794 A good and pure conscience is enlightened by true faith, for charity proceeds at the same time "from a pure heart and a good conscience and sincere faith." 60
The more a correct conscience prevails, the more do persons and groups turn aside from blind choice and try to be guided by objective standards of moral conduct. 61
1795 "Conscience is man's most secret core, and his sanctuary. There he is alone with God whose voice echoes in his depths" (GS 16).
1796 Conscience is a judgment of reason by which the human person recognizes the moral quality of a concrete act.
1797 For the man who has committed evil, the verdict of his conscience remains a pledge of conversion and of hope.
1798 A well-formed conscience is upright and truthful. It formulates its judgments according to reason, in conformity with the true good willed by the wisdom of the Creator. Everyone must avail himself of the means to form his conscience.
1799 Faced with a moral choice, conscience can make either a right judgment in accordance with reason and the divine law or, on the contrary, an erroneous judgment that departs from them.
1800 A human being must always obey the certain judgment of his conscience.
1801 Conscience can remain in ignorance or make erroneous judgments. Such ignorance and errors are not always free of guilt.
1802 The Word of God is a light for our path. We must assimilate it in faith and prayer and put it into practice. This is how moral conscience is formed.
English Translation of the Cathechism of the Catholic Church for the United States of America © 1997, United States Catholic Conference, Inc.