6. The Mystery of the Incarnation and of the Trinity are to be faithfully preserved and expounded. What is expressed in the documents of the Councils referred to above, concerning the one and the same Christ the Son of God, begotten before the ages in his divine nature and in time in his human nature, and also concerning the eternal persons of the Most Holy Trinity, belongs to the immutable truth of the Catholic faith.
This certainty does not prevent the Church in her awareness of the progress of human thought from considering that it is her duty to take steps to have the aforesaid mysteries continually examined by contemplation and by theological examination and to have them more fully expounded in up to date terminology. But while the necessary duty of investigation is being pursued, diligent care must be taken that these profound mysteries do not be interpreted in a meaning other than that in which “the Church has understood and understands them” (18).
The unimpaired truth of these mysteries is of the greatest moment for the whole Revelation of Christ, because they pertain to its very core, in such a way indeed that if they are undermined, the rest of the treasure of Revelation is falsified. The truth of these same mysteries is of no less concern to the Christian way of life both because nothing so effectively manifests the charity of God, to which the whole of Christian life should be a response, as does the Incarnation of the Son of God, our Redeemer (19), and also because “through Christ, the Word made flesh, men have access to the Father in the Holy Spirit and are made partakers of the divine nature” (20).
7. With regard to the truths which the present Declaration is safeguarding, it pertains to the Pastors of the Church to see that there is unity in professing the faith on the part of their people, and especially on the part of those who by mandate received from the Magisterium teach the sacred sciences or preach the word of God. This function of the Bishops belongs to the office divinely committed to them “of keeping pure and whole”… “the deposit of faith” in common with the Successor of Peter and “of proclaiming the Gospel without ceasing” (21); and by reason of this same office they are bound not to permit that ministers of the word of God, deviating from the way of sound doctrine, should pass it on corrupted or incomplete (22). The people, committed as they are to the care of the Bishops who “have to render account to God” (23) for them, enjoy “the sacred and inalienable right of receiving the word of God, the whole word of God, into which the Church does not cease to penetrate ever more profoundly” (24).
The faithful, then, and above all the theologians because of their important office and necessary function in the Church, must make faithful profession of the mysteries which this Declaration reaffirms. In like manner, by the movement and illumination of the Holy Spirit, the sons of the Church must hold fast to the whole teaching of the faith under the leadership of their Pastors and of the Pastor of the universal Church (25) “so that, in holding, practising and professing the faith that has been handed down, a common efforts results on the part of the Bishops and faithful” (26).