His Holiness Pope Pius XII
Encyclical Letter Concerning Some False OpinionsWhich Threaten to Undermine the Foundations of Catholic Doctrine
August 12, 1950
To Our Venerable Brethren, Patriarchs, Primates, Archbishops, Bishops and Other Local Ordinaries Enjoying Peace and Communion With the Holy See. Venerable Brethren, Greetings and Apostolic Benediction!
1). Disagreement and error among men on moral and religious matters have always been a cause of profound sorrow to all good men, but above all to the true and loyal sons of the church, especially today, when we see the principles of Christian culture being attacked on all sides.
2. It is not surprising that such discord and error should always have existed outside the fold of Christ. For though, absolutely speaking, human reason by its own natural force and light can arrive at a true and certain knowledge of the one personal God, Who by His providence watches over and governs the world, and also of the natural law, which the Creator has written in our hearts, still there are not a few obstacles to prevent reason from making efficient and fruitful use of its natural ability. The truths that have to do with God and the relations between God and men, completely surpass the sensible order and demand self-surrender and self-abnegation in order to be put into practice and to influence practical life. Now the human intellect, in gaining the knowledge of such truths is hampered both by the activity of the senses and the imagination, and by evil passions arising from original sin. Hence men easily persuade themselves in such matters that what they do not wish to believe is false or at least doubtful.
3. It is for this reason that divine revelation must be considered morally necessary so that those religious and moral truths which are not of their nature beyond the reach of reason in the present condition of the human race, may be known by all men readily -- with a firm certainty and with freedom from all error.
4. Furthermore the human intelligence sometimes experiences difficulties in forming a judgment about the credibility of the Catholic faith, notwithstanding the many wonderful external signs God has given, which are sufficient to prove with certitude by the natural light of reason alone the divine origin of the Christian religion. For man can, whether from prejudice or passion or bad faith, refuse and resist not only the evidence of the external proofs that are available, but also the impulses of actual grace.