From Pope St. John Paul II’s encyclical Veritatis Splendor (1993):
The moral theologian must therefore exercise careful discernment in the context of today’s prevalently scientific and technical culture, exposed as it is to the dangers of relativism, pragmatism and positivism. From the theological viewpoint, moral principles are not dependent upon the historical moment in which they are discovered. Moreover, the fact that some believers act without following the teachings of the Magisterium, or erroneously consider as morally correct a kind of behaviour declared by their Pastors as contrary to the law of God, cannot be a valid argument for rejecting the truth of the moral norms taught by the Church. The affirmation of moral principles is not within the competence of formal empirical methods. While not denying the validity of such methods, but at the same time not restricting its viewpoint to them, moral theology, faithful to the supernatural sense of the faith, takes into account first and foremost the spiritual dimension of the human heart and its vocation to divine love.
In fact, while the behavioural sciences, like all experimental sciences, develop an empirical and statistical concept of “normality”, faith teaches that this normality itself bears the traces of a fall from man’s original situation — in other words, it is affected by sin. Only Christian faith points out to man the way to return to “the beginning” (cf. Mt 19:8), a way which is often quite different from that of empirical normality. Hence the behavioural sciences, despite the great value of the information which they provide, cannot be considered decisive indications of moral norms. It is the Gospel which reveals the full truth about man and his moral journey, and thus enlightens and admonishes sinners; it proclaims to them God’s mercy, which is constantly at work to preserve them both from despair at their inability fully to know and keep God’s law and from the presumption that they can be saved without merit. God also reminds sinners of the joy of forgiveness, which alone grants the strength to see in the moral law a liberating truth, a grace-filled source of hope, a path of life.
— Veritatis Splendor 112