"[R]ejection of the Church's authority and her teaching . . . can be at the source of errors of judgment in moral conduct."  RCC Art. 1792.

Further, the primacy of conscience is rooted in the capacity of right reason to discern objective truth, expressed by God when we meet him in utter good faith in the confessional of our own minds.  "Conscience is the inner core of human beings whereby, compelled to seek the truth, they recognise the objective standards of moral conduct, indeed the dictates of God's law, and make a practical judgment of what is to be 
done here and now in applying those standards (Rom 2:15-16; Vatican II, On Religious Liberty (1965), §§2,3; The Church in the Modern World (1965), §16)."  Fr. Anthony Fischer, O.P.