Libertas §26

²⁶ But with no less religious care must we preserve that great and sacred treasure of the truths which God Himself has taught us. By many and convincing arguments, often used by defenders of Christianity, certain leading truths have been laid down: namely, that some things have been revealed by God; that the only-begotten Son of God was made flesh, to bear witness to the truth; that a perfect society was founded by Him - the Church, namely, of which He is the head, and with which He has promised to abide till the end of the world. To this society He entrusted all the truths which He had taught, in order that it might keep and guard them and with lawful authority explain them; and at the same time He commanded all nations to hear the voice of the Church, as if it were His own, threatening those who would nor hear it with everlasting perdition. Thus, it is manifest that man's best and surest teacher is God, the Source and Principle of all truth; and the only-begotten Son, who is in the bosom of the Father, the Way, the Truth, and the Life, the true Light which enlightens every man, and to whose teaching all must submit: "And they shall all be taught of God."(8)