Gaudium et Spes recognizes, as taught in another document of Vatican II, that is obligatory to rightly form a conscience, which for a Catholic particularly means particular attention to the Church’s teaching:

“Hence the more right conscience holds sway, the more persons and groups turn aside from blind choice and strive to be guided by the objective norms of morality. Conscience frequently errs from invincible ignorance without losing its dignity. The same cannot be said for a man who cares but little for truth and goodness, or for a conscience which by degrees grows practically sightless as a result of habitual sin.”

“But in their manner of acting, spouses should be aware that they cannot proceed arbitrarily, but must always be governed according to a conscience dutifully conformed to the divine law itself, and should be submissive toward the Church's teaching office, which authentically interprets that law in the light of the Gospel.”