It is worthwhile gathering the key magisterial texts on the matter. In I cited many passages from scripture and many statements from the Fathers of the first two centuries of the Church, before Origen introduced the universalist novelty. Many more statements from the Fathers of later centuries could be cited, as well as many statements from the Doctors of the Church. In Catholic theology, that the Fathers and Doctors are nearly unanimous on some point of doctrine by itself gives it enormous weight, even apart from formal magisterial pronouncements. But here I will just concentrate on magisterial statements and related texts.
Some critics of the previous post objected to its “Denzinger theology” style of piling up quotations, and will no doubt object to my piling up some more in this post. But like most critics of this style, they miss the point. Yes, a deep understanding of Catholic doctrine cannot be had merely by accumulating and reiterating formulas from the past. But before you can probe Catholic doctrine at depth, you first have to know what it is. And noting that a doctrine has for millennia been reiterated consistently, especially in scripture, the teaching of the Fathers and Doctors, creeds, conciliar pronouncements, papal statements, catechisms, etc. is an excellent way of determining that. “Denzinger theology” is not the last word, but it must always be the first word. It determines the boundaries within which orthodox theological discussion must take place.
I have not tried to be comprehensive. In particular, I have not quoted every magisterial statement on the reality and nature of hell, but only the statements clearly asserting or implying the falsity of the universalist claim that none can be damned forever:
Pope St. Anastasius I (399-401):
The reverend and honourable Theophilus our brother and fellow-bishop, ceases not to watch over the things that make for salvation, that God's people in the different churches may not by reading Origen run into awful blasphemies.
Being informed, then, by a letter of the aforesaid bishop, we inform your holiness… to the end that no man may contrary to the commandment read these books which we have mentioned, have condemned the same… [W]e have intimated that everything written in days gone by by Origen that is contrary to our faith is also rejected and condemned by us.
I send this letter to your holiness by the hand of the presbyter Eusebius, a man filled with a glowing faith and love for the Lord. He has shewn to me some blasphemous chapters which made me shudder as I passed judgement on them. If Origen has put forth any other writings, you are to know that they and their author are alike condemned by me. (Letter to Simplicianus)
The credal formula Fides Damasi (or “Faith of Damasus”) (5th century):
It is our hope that we shall receive from him eternal life, the reward of good merit, or else (we shall) receive the penalty of eternal punishment for sins.
The Athanasian Creed (5th century):
Whosoever will be saved, before all things it is necessary that he hold the Catholic Faith. Which Faith except everyone do keep whole and undefiled, without doubt he shall perish everlastingly…
He sitteth on the right hand of the Father, God Almighty, from whence he shall come to judge the quick and the dead. At whose coming all men shall rise again with their bodies, and shall give account for their own works. And they that have done good shall go into life everlasting, and they that have done evil into everlasting fire. This is the Catholic Faith, which except a man believe faithfully and firmly, he cannot be saved.
Pope Vigilius (537-55):
If anyone says or holds that the punishment of the demons and of impious men is temporary, and that it will have an end at some time, that is to say, there will be a complete restoration of the demons or of impious men, let him be anathema. (Canons against Origen)
Pope Innocent III (1198-1216):
The punishment of original sin is the deprivation of the vision of God, but the punishment of actual sin is the torment of eternal hell. (Maiores Ecclesiae Causas)
Fourth Lateran Council (1215):
He will come at the end of time to judge the living and the dead, to render to every person according to his works, both to the reprobate and to the elect. All of them will rise with their own bodies, which they now wear, so as to receive according to their deserts, whether these be good or bad; for the latter perpetual punishment with the devil, for the former eternal glory with Christ.
Pope Innocent IV (1243-54):
But if anyone dies unrepentant in the state of mortal sin, he will undoubtedly be tormented forever in the fires of an everlasting hell. (Letter to the Bishop of Tusculum)
The Council of Trent (1545-63):
The council texts concerning justification make reference in several places to “eternal punishment” (Session VI, Chapter 14 and Canons 25 and 30), and those concerning penance refer to “the loss of eternal happiness, and the incurring of eternal damnation” (Session XIV, Canon 5).
In addition, the falsity of universalist claims to the effect that we cannot forever resist God’s grace and that we can be assured that we will ultimately be saved is implied by the following passages:
In adults the beginning of justification must be attributed to God’s prevenient grace through Jesus Christ… In this way, God touches the heart of man with the illumination of the Holy Spirit, but man himself is not entirely inactive while receiving that inspiration, since he can reject it. (Session VI, Chapter 5)
If anyone says that the free will of man, moved and awakened by God, in no way cooperates by an assent to God’s awakening call… and that man cannot refuse his assent if he wishes, but that like a lifeless object he does nothing at all and is merely passive, let him be anathema. (Session VI, Canon 4)
If anyone says that he has absolute and infallible certitude that he will surely have the great gift of perseverance to the end, unless he has learned this by a special revelation, let him be anathema. (Session VI, Canon 16)
The Roman Catechism, promulgated by Pope St. Pius V (1566):
Turning next to those who shall stand on His left, He will pour out His justice upon them in these words: Depart from me, ye cursed, into everlasting fire, prepared for the devil and his angels.
The first words, depart from me, express the heaviest punishment with which the wicked shall be visited, their eternal banishment from the sight of God, unrelieved by one consolatory hope of ever recovering so great a good. This punishment is called by theologians the pain of loss, because in hell the wicked shall be deprived forever of the light of the vision of God.
The words ye cursed, which follow, increase unutterably their wretched and calamitous condition. If when banished from the divine presence they were deemed worthy to receive some benediction, this would be to them a great source of consolation. But since they can expect nothing of this kind as an alleviation of their misery, the divine justice deservedly pursues them with every species of malediction, once they have been banished.
The next words, into everlasting fire, express another sort of punishment, which is called by theologians the pain of sense, because, like lashes, stripes or other more severe chastisements, among which fire, no doubt, produces the most intense pain, it is felt through the organs of sense. When, moreover, we reflect that this torment is to be eternal, we can see at once that the punishment of the damned includes every kind of suffering.
The concluding words, which was prepared for the devil and his angels, make this still more clear. For since nature has so provided that we feel miseries less when we have companions and sharers in them who can, at least in some measure, assist us by their advice and kindness, what must be the horrible state of the damned who in such calamities can never separate themselves from the companionship of most wicked demons? (McHugh and Callan translation, pp. 85-86)
For sin deprives us of the friendship of God, to whom we are indebted for so many invaluable blessings, and from whom we might have expected and received gifts of still higher value; and along with this it consigns us to eternal death and to torments unending and most severe. (p. 281)
Catechism of Pope St. Pius X (1908):
The Angels banished for ever from Paradise and condemned to hell are called demons, and their chief is called Lucifer or Satan…
The Last Article of the Creed teaches us that, after the present life there is another life, eternally happy for the elect in heaven, or eternally miserable for the damned in hell…
The misery of the damned consists in being for ever deprived of the vision of God and punished with eternal torments in hell.
After the resurrection of the flesh, man in the fullness of his nature, that is, in body and in soul, will be for ever happy or for ever tormented…
The bliss of heaven in the case of the blessed, and the miseries of hell in the case of the damned, will be the same in substance and in eternal duration; but in measure, or degree, they will be greater or less according to the extent of each one's merits or demerits.
Pope Pius XII (1939-58):
The revelation and the magisterium of the Church firmly establish that after the end of this earthly life, those who are guilty of grave sin will receive from the Supreme Lord a judgment and an execution of punishment, from which there is no liberation or pardon… The fact of the immutability and eternity of the judgment of damnation and its execution is beyond any discussion… The Supreme Legislator… has decreed that the validity of his judgment and its execution will never cease. Therefore, its duration remains fixed without any limitations. (Address to the Union of Italian Catholic Jurists of February 5, 1955, quoted in Francis Sola and Joseph Sagües, Sacrae Theologiae Summa IVB, translated by Kenneth Baker, S.J, at pp. 376-377)
Pope St. John Paul II (1978-2005):
In point of fact, the ancient councils rejected the theory of the “final apocatastasis,” according to which the world would be regenerated after destruction, and every creature would be saved; a theory which indirectly abolished hell. But the problem remains. Can God, who has loved man so much, permit the man who rejects him to be condemned to eternal torment? And yet, the words of Christ are unequivocal. In Matthew’s Gospel he speaks clearly of those who will go to eternal punishment. (Crossing the Threshold of Hope, p. 185)
(While Crossing the Threshold of Hope is not a magisterial document, it is worth citing as evidence of the pope’s thinking on this topic.)
Catechism of the Catholic Church, promulgated by Pope St. John Paul II (1992):
The teaching of the Church affirms the existence of hell and its eternity. Immediately after death the souls of those who die in a state of mortal sin descend into hell, where they suffer the punishments of hell, “eternal fire.” The chief punishment of hell is eternal separation from God, in whom alone man can possess the life and happiness for which he was created and for which he longs. (sec. 1035)
Compendium of the Catechism of the Catholic Church, promulgated by Pope Benedict XVI (2005):
Satan and the other demons, about which Sacred Scripture and the Tradition of the Church speak, were angels, created good by God. They were, however, transformed into evil because with a free and irrevocable choice they rejected God and his Kingdom, thus giving rise to the existence of hell. (sec. 74)
Hell consists in the eternal damnation of those who die in mortal sin through their own free choice. The principal suffering of hell is eternal separation from God in whom alone we can have the life and happiness for which we were created and for which we long. Christ proclaimed this reality with the words, “Depart from me, you cursed, into the eternal fire” (Matthew 25:41). (sec. 212)
The final or universal judgment consists in a sentence of happiness or eternal condemnation, which the Lord Jesus will issue in regard to the “just and the unjust” (Acts 24:15) when he returns as the Judge of the living and the dead. (sec. 214)