Fides et Ratio §50

⁵⁰ In the light of faith, therefore, the Church's Magisterium can and must authoritatively exercise a critical discernment of opinions and philosophies which contradict Christian doctrine. It is the task of the Magisterium in the first place to indicate which philosophical presuppositions and conclusions are incompatible with revealed truth, thus articulating the demands which faith's point of view makes of philosophy. Moreover, as philosophical learning has developed, different schools of thought have emerged. This pluralism also imposes upon the Magisterium the responsibility of expressing a judgement as to whether or not the basic tenets of these different schools are compatible with the demands of the word of God and theological enquiry. It is the Church's duty to indicate the elements in a philosophical system which are incompatible with her own faith. In fact, many philosophical opinions—concerning God, the human being, human freedom and ethical behaviour— engage the Church directly, because they touch on the revealed truth of which she is the guardian. In making this discernment, we Bishops have the duty to be “witnesses to the truth”, fulfilling a humble but tenacious ministry of service which every philosopher should appreciate, a service in favour of recta ratio , or of reason reflecting rightly upon what is true.