2. Profession of the Christian faith is not intelligible without strong, lively apostolic fervor; in fact, "everyone is bound to proclaim his faith to others, either to give good example and encouragement to the rest of the faithful, or to check the attacks of unbelievers," especially in our time, when the universal Church and human society are beset by many difficulties. Anyone who deems himself a Christian must know that he is bound by his conscience to the basic, imperative duty of bearing witness to the truth in which he believes and to the grace which has transformed his soul. (Papal Encyclical, Princeps Pastorum, November 1959).
3. Sure of her competence as the bearer of the Revelation of Jesus Christ, the Church reaffirms the need to reflect upon truth. This is why I have decided to address you, my venerable Brother Bishops, with whom I share the mission of "proclaiming the truth openly" (2 Cor 4:2), as also theologians and philosophers whose duty it is to explore the different aspects of truth, and all those who are searching; and I do so in order to offer some reflections on the path which leads to true wisdom, so that those who love truth may take the sure path leading to it and so find rest from their labours and joy for their spirit. (Papal Encyclical, Fides et Ratio, 14 September 1998).
This charity, intelligent and sympathetic towards those even who offend you, does by no means imply a renunciation of the right of proclaiming, vindicating and defending the truth and its implications. The priest's first loving gift to his neighbors is to serve truth and refute error in any of its forms. Failure on this score would be not only a betrayal of God and your vocation, but also an offense against the real welfare of your people and country. (Papal Encyclical, Mit Brennender Sorge, 14 March 1937).