Dogmatic Constitution "Dei Filius"
Chap. 1. God, Creator of All Things
The holy, Catholic, Apostolic, Roman Church believes and confesses that there is one, true, living God, Creator and Lord of heaven and earth, omnipotent, eternal, immense, incomprehensible, infinite in intellect and will, and in every perfection; who, although He is one, singular, altogether simple and unchangeable spiritual substance, must be proclaimed distinct in reality and essence from the world; most blessed in Himself and of Himself, and ineffably most high above all things which are or can be conceived outside Himself.
This sole true God by His goodness and "omnipotent power," not to increase His own beatitude, and not to add to, but to manifest His perfection by the blessings which He bestows on creatures, with most free volition, "immediately from the beginning of time fashioned each creature out of nothing, spiritual and corporeal, namely angelic and mundane; and then the human creation, common as it were, composed of both spirit and body" [Lateran Council IV, ch. 1]
But God protects and governs by His providence all things which He created, "reaching from end to end mightily and ordering all things sweetly" [cf. Wis 8:1]. For "all things are naked and open to His eyes" [Heb 4:13], even those which by the free action of creatures are in the future.
Chap. 2. Revelation
The same Holy Mother Church holds and teaches that God, the beginning and end of all things, can be known with certitude by the natural light of human reason from created things; "for the invisible things of him, from the creation of the world, are clearly seen, being understood by the things that are made" [ Rom 1:20]; nevertheless, it has pleased His wisdom and goodness to reveal Himself and the eternal decrees of His will to the human race in another and supernatural way, as the Apostle says: "God, who at sundry times and in divers manners, spoke in times past to the fathers by the prophets, last of all, in these days hath spoken to us by His Son" [Heb 1:1 f].
Indeed, it must be attributed to this divine revelation that those things, which in divine things are not impenetrable to human reason by itself, can, even in this present condition of the human race, be known readily by all with firm certitude and with no admixture of error. Nevertheless, it is not for this reason that revelation is said to be absolutely necessary, but because God in His infinite goodness has ordained man for a supernatural end, to participation, namely, in the divine goods which altogether surpass the understanding of the human mind, since "eye hath not seen, nor ear heard, neither hath it entered into the heart of man, what things God hath prepared for them that love Him" [1Cor 2:9].
Furthermore, this supernatural revelation, according to the faith of the universal Church, as declared by the holy synod of Trent, is contained "in the written books and in the unwritten traditions which have been received by the apostles from the mouth of Christ Himself; or, through the inspiration of the Holy Spirit have been handed down by the apostles themselves, and have thus come to us" [Council of Trent]. And, indeed, these books of the Old and New Testament, whole with all their parts, just as they were enumerated in the decree of the same Council, are contained in the older Vulgate Latin edition, and are to be accepted as sacred and canonical. But the Church holds these books as sacred and canonical, not because, having been put together by human industry alone, they were then approved by its authority; nor because they contain revelation without error; but because, having been written by the inspiration of the Holy Spirit, they have God as their author and, as such, they have been handed down to the Church itself.
But, since the rules which the holy Synod of Trent salutarily decreed concerning the interpretation of Divine Scripture in order to restrain impetuous minds, are wrongly explained by certain men, We, renewing the same decree, declare this to be its intention: that, in matters of faith and morals pertaining to the instruction of Christian Doctrine, that must be considered as the true sense of Sacred Scripture which Holy Mother Church has held and holds, whose office it is to judge concerning the true understanding and interpretation of the Sacred Scriptures; and, for that reason, no one is permitted to interpret Sacred Scripture itself contrary to this sense, or even contrary to the unanimous agreement of the Fathers.
Chap. 3. Faith
Since man is wholly dependent on God as his Creator and Lord, and since created reason is completely subject to uncreated truth, we are bound by faith to give full obedience of intellect and will to God who reveals. But the Catholic Church professes that this faith, which is the beginning of human salvation, is a supernatural virtue by which we, with the aid and inspiration of the grace of God, believe that the things revealed by Him are true, not because the intrinsic truth of the revealed things has been perceived by the natural light of reason, but because of the authority of God Himself who reveals them, who can neither deceive nor be deceived. For, "faith is," as the Apostle testifies, "the substance of things to be hoped for, the evidence of things that appear not" [Heb 11:1].
However, in order that the "obedience" of our faith should be "consonant with reason" [cf. Rom 12:1], God has willed that to the internal aids of the Holy Spirit there should be joined external proofs of His revelation, namely: divine facts, especially miracles and prophecies which, because they clearly show forth the omnipotence and infinite knowledge of God, are most certain signs of a divine revelation, and are suited to the intelligence of all. Wherefore, not only Moses and the prophets, but especially Christ the Lord Himself, produced many genuine miracles and prophecies; and we read concerning the apostles: "But they going forth preached everywhere: the Lord working withal and confirming the word with signs that followed" [Mk 16:20]. And again it is written: "And we have the more firm prophetical word: whereunto you do well to attend, as to a light that shineth in a dark place" [2Pet 1:19].
Moreover, although the assent of faith is by no means a blind movement of the intellect, nevertheless, no one can "assent to the preaching of the Gospel," as he must to attain salvation, "without the illumination and inspiration of the Holy Spirit, who gives to all a sweetness in consenting to and believing in truth" (Council of Orange). Wherefore, "faith" itself in itself, even if it "worketh not by charity" [cf. Gal 5:6], is a gift of God, and its act is a work pertaining to salvation, by which man offers a free obedience to God Himself by agreeing to, and cooperating with His grace, which he could resist.
Further, by divine and Catholic faith, all those things must be believed which are contained in the written word of God and in tradition, and those which are proposed by the Church, either in a solemn pronouncement or in her ordinary and universal teaching power, to be believed as divinely revealed.
But, since "without faith it is impossible to please God" [Heb 11:6] and to attain to the fellowship of His sons, hence, no one is justified without it; nor will anyone attain eternal life except "he shall persevere unto the end on it" [Mt 10:22; 24:13]. Moreover, in order that we may satisfactorily perform the duty of embracing the true faith and of continuously persevering in it, God, through His only-begotten Son, has instituted the Church, and provided it with clear signs of His institution, so that it can be recognized by all as the guardian and teacher of the revealed word.
For, to the Catholic Church alone belong all those many and marvelous things which have been divinely arranged for the evident credibility of the Christian faith. But, even the Church itself by itself, because of its marvelous propagation, its exceptional holiness, and inexhaustible fruitfulness in all good works; because of its catholic unity and invincible stability, is a very great and perpetual motive of credibility, and an incontestable witness of its own divine mission.
By this it happens that the Church as "a standard set up unto the nations" [Is 11:12], both invites to itself those who have not yet believed, and makes its sons more certain that the faith, which they profess, rests on a very firm foundation. Indeed, an efficacious aid to this testimony has come from supernatural virtue. For, the most benign God both excites the erring by His grace and aids them so that they can "come to a knowledge of the truth" [1Tim 2:4], and also confirms in His grace those whom "He has called out of darkness into his marvelous light" [1Pet 2:9], so that they may persevere in this same light, not deserting if He be not deserted. Wherefore, not at all equal is the condition of those, who, through the heavenly gift of faith, have adhered to the Catholic truth, and of those, who, led by human opinions, follow a false religion; for, those who have accepted the faith under the teaching power of the Church can never have a just cause of changing or doubting that faith. Since this is so, "giving thanks to God the Father, who hath made us worthy to be partakers of the lot of the saints in light" [Col 1:12], let us not neglect such salvation, but "looking on Jesus, the author and finisher of faith" [Heb 12:2], "let us hold fast the confession of our hope without wavering" [Heb 10:23].
Chap. 4. Faith and reason
By enduring agreement the Catholic Church has held and holds that there is a twofold order of knowledge, distinct not only in principle but also in object: (1) in principle, indeed, because we know in one way by natural reason, in another by divine faith; (2) in object, however, because, in addition to things to which natural reason can attain, mysteries hidden in God are proposed to us for belief which, had they not been divinely revealed, could not become known. Wherefore, the Apostle, who testifies that God was known to the Gentiles "by the things that are made" [Rom 1:20], nevertheless, when discoursing about grace and truth which "was made through Jesus Christ" [cf. Jn 1:17] proclaims: "We speak the wisdom of God in a mystery, a wisdom which is hidden, which God ordained before the world, unto our glory, which none of the princes of this world know. […] But to us God hath revealed them by His Spirit For the Spirit searcheth all things, yea the deep things of God" [1Cor 2:7,8,10]. And the Only-begotten Himself "confesses to the Father, because He hath hid these things from the wise and prudent, and hath revealed them to little ones" [cf. Mt 11:25]
And, indeed, reason illustrated by faith, when it zealously, piously, and soberly seeks, attains with the help of God some understanding of the mysteries, and that a most profitable one, not only from the analogy of those things which it knows naturally, but also from the connection of the mysteries among themselves and with the last end of man; nevertheless, it is never capable of perceiving those mysteries in the way it does the truths which constitute its own proper object. For, divine mysteries by their nature exceed the created intellect so much that, even when handed down by revelation and accepted by faith, they nevertheless remain covered by the veil of faith itself, and wrapped in a certain mist, as it were, as long as in this mortal life, "we are absent from the Lord: for we walk by faith and not by sight" [2Cor 5:6 f.],
But, although faith is above reason, nevertheless, between faith and reason no true dissension can ever exist, since the same God, who reveals mysteries and infuses faith, has bestowed on the human soul the light of reason; moreover, God cannot deny Himself, nor ever contradict truth with truth. But, a vain appearance of such a contradiction arises chiefly from this, that either the dogmas of faith have not been understood and interpreted according to the mind of the Church, or deceitful opinions are considered as the determinations of reason. Therefore, "every assertion contrary to the truth illuminated by faith, we define to be altogether false" [Lateran Council V].
Further, the Church which, together with the apostolic duty of teaching, has received the command to guard the deposit of faith, has also, from divine Providence, the right and duty of proscribing "knowledge falsely so called" [1Tim 6:20], "lest anyone be cheated by philosophy and vain deceit" [cf. Col 2:8]. Wherefore, all faithful Christians not only are forbidden to defend opinions of this sort, which are known to be contrary to the teaching of faith, especially if they have been condemned by the Church, as the legitimate conclusions of science, but they shall be altogether bound to hold them rather as errors, which present a false appearance of truth.
And, not only can faith and reason never be at variance with one another, but they also bring mutual help to each other, since right reasoning demonstrates the basis of faith and, illumined by its light, perfects the knowledge of divine things, while faith frees and protects reason from errors and provides it with manifold knowledge. Wherefore, the Church is so far from objecting to the culture of the human arts and sciences, that it aids and promotes this cultivation in many ways. For, it is not ignorant of, nor does it despise the advantages flowing therefrom into human life; nay, it confesses that, just as they have come forth from "God, the Lord of knowledge" [1Sam 2:3], so, if rightly handled, they lead to God by the aid of His grace. And it (the Church) does not forbid disciplines of this kind, each in its own sphere, to use its own principles and its own method; but, although recognizing this freedom, it continually warns them not to fall into errors by opposition to divine doctrine, nor, having transgressed their own proper limits, to be busy with and to disturb those matters which belong to faith.
For, the doctrine of faith which God revealed has not been handed down as a philosophic invention to the human mind to be perfected, but has been entrusted as a divine deposit to the Spouse of Christ, to be faithfully guarded and infallibly interpreted. Hence, also, that understanding of its sacred dogmas must be perpetually retained, which Holy Mother Church has once declared; and there must never be recession from that meaning under the specious name of a deeper understanding "Therefore […] let the understanding, the knowledge, and wisdom of individuals as of all, of one man as of the whole Church, grow and progress strongly with the passage of the ages and the centuries; but let it be solely in its own genus, namely in the same dogma, with the same sense and the same understanding.'' [Vincent of Lerins, Commonitorium, 23, 3].
Original Latin text in H. DENZINGER, Enchiridion Simbolorum, definitionum et declarationum de rebus fidei et morum, ed. by P. Hünermann (Freiburg i.B.: Herder, 1991), DH 3001-3020. English translation provided by Welcome to Catholic Church, Harmony Media inc.