The Catechism of the Catholic Church is very badly wrong on “conscience”.
Here are the two passages that very wrongly give conscience absolute power. They explicitly state without doubt that conscience must always be followed…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.
1800 A human being must always obey the certain judgment of his conscience.
These two passages are rightly and directly contradicted by the encyclical VERITATIS SPLENDOR by Pope John Paul II which say that intrinsic evil i.e. abortion/murder can never be permitted by conscience.
VERITATIS SPLENDOR…
52 The negative precepts of the natural law are universally valid. They oblige each and every individual, always and in every circumstance. It is a matter of prohibitions which forbid a given action semper et pro semper, without exception, because the choice of this kind of behaviour is in no case compatible with the goodness of the will of the acting person, with his vocation to life with God and to communion with his neighbour. It is prohibited — to everyone and in every case — to violate these precepts. They oblige everyone, regardless of the cost, never to offend in anyone, beginning with oneself, the personal dignity common to all.
58. The importance of this interior dialogue of man with himself can never be adequately appreciated. But it is also a dialogue of man with God, the author of the law, the primordial image and final end of man. Saint Bonaventure teaches that "conscience is like God's herald and messenger; it does not command things on its own authority, but commands them as coming from God's authority, like a herald when he proclaims the edict of the king. This is why conscience has binding force".103
59 The Church has always taught that one may never choose kinds of behaviour prohibited by the moral commandments expressed in negative form in the Old and New Testaments. As we have seen, Jesus himself reaffirms that these prohibitions allow no exceptions: "If you wish to enter into life, keep the commandments... You shall not murder, You shall not commit adultery, You shall not steal, You shall not bear false witness" (Mt 19:17-18).52
90. The relationship between faith and morality shines forth with all its brilliance in the unconditional respect due to the insistent demands of the personal dignity of every man, demands protected by those moral norms which prohibit without exception actions which are intrinsically evil.