" It seems therefore that we have a conflict between two antithetical models, morality of conscience and morality of authority. The freedom of the Christian is safeguarded by the primal proposition of the moral tradition, that the conscience is the highest norm and that one must follow it even against authority. When authority—in this case the Church’s magisterium—speaks on matters of morality, it supplies material that helps the conscience form its own judgment, but ultimately it is only conscience that has the last word. Some authors express this ultimately decisive authority of conscience by saying that conscience is infallible.1 "

― Benedict XVI , Values in a Time of Upheaval