Humani Generis §21

²¹ It is also true that theologians must always return to the sources of divine revelation: for it belongs to them to point out how the doctrine of the living Teaching Authority is to be found either explicitly or implicitly in the Scriptures and in Tradition. Besides, each source of divinely revealed doctrine contains so many rich treasures of truth, that they can really never be exhausted. Hence it is that theology through the study of its sacred sources remains ever fresh; on the other hand, speculation which neglects a deeper search into the deposit of faith, proves sterile, as we know from experience. But for this reason even positive theology cannot be on a par with merely historical science. For, together with the sources of positive theology God has given to His Church a living Teaching Authority to elucidate and explain what is contained in the deposit of faith only obscurely and implicitly. This deposit of faith our Divine Redeemer has given for authentic interpretation not to each of the faithful, not even to theologians, but only to the Teaching Authority of the Church. But if the Church does exercise this function of teaching, as she often has through the centuries, either in the ordinary or in the extraordinary way, it is clear how false is a procedure which would attempt to explain what is clear by means of what is obscure. Indeed, the very opposite procedure must be used. Hence Our Predecessor of immortal memory, Pius IX, teaching that the most noble office of theology is to show how a doctrine defined by the Church is contained in the sources of revelation, added these words, and with very good reason: "in that sense in which it has been defined by the Church."