Humani Generis §30

³⁰ Of course this philosophy deals with much that neither directly nor indirectly touches faith or morals, and which consequently the Church leaves to the free discussion of experts. But this does not hold for many other things, especially those principles and fundamental tenets to which We have just referred. However, even in these fundamental questions, we may clothe our philosophy in a more convenient and richer dress, make it more vigorous with a more effective terminology, divest it of certain scholastic aids found less useful, prudently enrich it with the fruits of progress of the human mind. But never may we overthrow it, or contaminate it with false principles, or regard it as a great, but obsolete, relic. For truth and its philosophic expression cannot change from day to day, least of all where there is question of self-evident principles of the human mind or of those propositions which are supported by the wisdom of the ages and by divine revelation. Whatever new truth the sincere human mind is able to find, certainly cannot be opposed to truth already acquired, since God, the highest Truth, has created and guides the human intellect, not that it may daily oppose new truths to rightly established ones, but rather that, having eliminated errors which may have crept in, it may build truth upon truth in the same order and structure that exist in reality, the source of truth. Let no Christian therefore, whether philosopher or theologian, embrace eagerly and lightly whatever novelty happens to be thought up from day to day, but rather let him weigh it with painstaking care and a balanced judgment, lest he lose or corrupt the truth he already has, with grave danger and damage to his faith.