We believe the Divine and Sacred Scriptures to be God-taught; and, therefore, we ought to believe the same without doubting; yet not otherwise than as the Catholic Church has interpreted and delivered the same. For every foul heresy accepts the Divine Scriptures, but perversely interprets the same, using metaphors, and homonymies, and sophistries of man’s wisdom, confounding what ought to be distinguished, and trifling with what ought not to be trifled with. For if [we were to accept Scriptures] otherwise, each man holding every day a different sense concerning them, the Catholic Church would not by the grace of Christ continue to be the Church until this day, holding the same doctrine of faith, and always identically and steadfastly believing. But rather she would be torn into innumerable parties, and subject to heresies. Neither would the Church be holy, the pillar and ground of the truth, (1 Timothy 3:15) without spot or wrinkle; (Eph. 5:27) but would be the Church of the malignant (Psalm 25:5) as it is obvious the church of the heretics undoubtedly is, and especially that of Calvin, who are not ashamed to learn from the Church, and then to wickedly repudiate her.
Wherefore, the witness also of the Catholic Church is, we believe, not of inferior authority to that of the Divine Scriptures. For one and the same Holy Spirit being the author of both, it is quite the same to be taught by the Scriptures and by the Catholic Church. Moreover, when any man speaks from himself he is liable to err, and to deceive, and be deceived; but the Catholic Church, as never having spoken, or speaking from herself, but from the Spirit of God — who being her teacher, she is ever unfailingly rich — it is impossible for her to in any wise err, or to at all deceive, or be deceived; but like the Divine Scriptures, is infallible, and has perpetual authority. (Decree 2)
We believe that the Catholic Church is taught by the Holy Spirit. For He is the true Paraclete; whom Christ sends from the Father, (cf. John 25:26) to teach the truth, (cf. John 26:13) and to drive away darkness from the minds of the Faithful. The teaching of the Holy Spirit, however, does not directly illuminate the Church, but [does so] through the holy Fathers and Leaders of the Catholic Church. All Scripture is, and is called, the word of the Holy Spirit, not that it was spoken directly by Him, but that it was spoken by Him through the Apostles and Prophets. In like manner the Church is taught indeed by the Life-giving Spirit, but through the medium of the holy Fathers and Doctors (whose rule is acknowledged to be the Holy and Ecumenical Synods; for we shall not cease to say this ten thousand times); and, therefore, not only are we persuaded, but do profess as true and undoubtedly certain, that it is impossible for the Catholic Church to err, or at all be deceived, or ever to choose falsehood instead of truth. For the All-holy Spirit continually operating through the holy Fathers and Leaders faithfully ministering, delivers the Church from error of every kind. (Decree 12)