But when we consider what was actually done we find that Jesus Christ did not, in point of fact, institute a Church to embrace several communities similar in nature, but in themselves distinct, and lacking those bonds which render the Church unique and indivisible after that manner in which in the symbol of our faith we profess: ‘I believe in one Church.’ (Leo XIII. Encyclical Satis cognitum, no. 4, June 29, 1896)

The Church is one because she has as her source and exemplar the unity of the Trinity of Persons in one God. As her Founder and Head, Jesus Christ re-established the unity of all people in one body. As her soul, the Holy Spirit unites all the faithful in communion with Christ. The Church has but one faith, one sacramental life, one apostolic succession, one common hope, and one and the same charity. (Compendium of the Catholic Church, no. 161)

And so I say to you, you are Peter, and upon this rock I will build my church, and the gates of the netherworld shall not prevail against it. I will give you the keys to the kingdom of heaven. Whatever you bind on earth shall be bound in heaven; and whatever you loose on earth shall be loosed in heaven. (Mt 16:18-19)

And I have given them the glory you gave me, so that they may be one, as we are one, I in them and you in me, that they may be brought to perfection as one, that the world may know that you sent me, and that you loved them even as you loved me. (Jn 17:22-23)

And he put all things beneath his feet and gave him as Head over all things to the Church, which is his body, the fullness of the one who fills all things in every way. (Eph 1:22-23)

For that virgin is the Church, the spouse of one husband Christ, who suffers herself to be corrupted by no error, so that through the whole world we have one entire and pure communion. (Leo I the Great. Letter 80, To Anatolius, Bishop of Constantinople, PL 54, 913)

For the birth of Christ is the source of life for Christian folk, and the birthday of the Head is the birthday of the body. Although every individual that is called has his own order, and all the sons of the Church are separated from one another by intervals of time, yet as the entire body of the faithful being born in the font of baptism is crucified with Christ in His passion, raised again in His resurrection, and placed at the Father’s right hand in His ascension, so with Him are they born in this nativity. For any believer in whatever part of the world that is re-born in Christ, quits the old paths of his original nature and passes into a new man by being re-born; and no longer is he reckoned of his earthly father’s stock but among the seed of the Saviour, Who became the Son of man in order that we might have the power to be the sons of God. (Leo I the Great. Sermon 26, II, On the Feast of the Nativity, PL 54, 213)

God is one, and Christ is one, and His Church is one, and the faith is one, and the people is joined into a substantial unity of body by the cement of concord. Unity cannot be severed; nor can one body be separated by a division of its structure, nor torn into pieces, with its entrails wrenched asunder by laceration. (Saint Cyprian of Carthage. The Unity of the Church, no. 23)

Only faith can recognize that the Church possesses these properties [one, holy, catholic and apostolic] from her divine source. But their historical manifestations are signs that also speak clearly to human reason. As the First Vatican Council noted, the ‘Church herself, with her marvelous propagation, eminent holiness, and inexhaustible fruitfulness in everything good, her catholic unity and invincible stability, is a great and perpetual motive of credibility and an irrefutable witness of her divine mission.’ (Vatican Council I: DS 3013) (Catechism of the Catholic Church, no. 812)

What are these bonds of unity? Above all, charity ‘binds everything together in perfect harmony’ (Col 3:14). But the unity of the pilgrim Church is also assured by visible bonds of communion: – profession of one faith received from the Apostles; common celebration of divine worship, especially of the sacraments; apostolic succession through the sacrament of Holy Orders, maintaining the fraternal concord of God’s family. (Catechism of the Catholic Church, no. 815)

This is the one Church of Christ which in the Creed is professed as one, holy, catholic and apostolic, which our Saviour, after His Resurrection, commissioned Peter to shepherd (Jn 21:17), and him and the other apostles to extend and direct with authority (Cf. Mt 28:18), which He erected for all ages as ‘the pillar and mainstay of the truth’ (1Tim. 3:15). (Vatican Council II. Dogmatic Constitution Lumen gentium, no. 8, November 21, 1964)

The Church, then, is God’s only flock; it is like a standard lifted high for the nations to see it: for it serves all mankind through the Gospel of peace as it makes its pilgrim way in hope toward the goal of the fatherland above. This is the sacred mystery of the unity of the Church, in Christ and through Christ, the Holy Spirit energizing its various functions. It is a mystery that finds its highest exemplar and source in the unity of the Persons of the Trinity: the Father and the Son in the Holy Spirit, one God. (Vatican Council II. Decree Unitatis redintegratio, no. 2, November 21, 1964)

In connection with the unicity and universality of the salvific mediation of Jesus Christ, the unicity of the Church founded by him must be firmly believed as a truth of Catholic faith. Just as there is one Christ, so there exists a single body of Christ, a single Bride of Christ: ‘a single Catholic and apostolic Church’ (cf. Mt 16:18, 28:20). Furthermore, the promises of the Lord that he would not abandon his Church and that he would guide her by his Spirit (cf. Jn 16:13) mean, according to Catholic faith, that the unicity and the unity of the Church — like everything that belongs to the Church’s integrity — will never be lacking. (Congregation for the Doctrine of the Faith. Declaration Dominus Iesus, no. 16, August 6, 2000)

And thus, just as the head and members of a living body, though not identical, are inseparable, so too Christ and the Church can neither be confused nor separated, and constitute a single ‘whole Christ’. This same inseparability is also expressed in the New Testament by the analogy of the Church as the Bride of Christ (cf. 2Cor 11:2, Eph 5:25-29; Rev 21:2, 9) (Congregation for the Doctrine of the Faith. Declaration Dominus Iesus, no. 16, August 6, 2000)

‘The Christian faithful are therefore not permitted to imagine that the Church of Christ is nothing more than a collection — divided, yet in some way one — of Churches and ecclesial communities; nor are they free to hold that today the Church of Christ nowhere really exists, and must be considered only as a goal which all Churches and ecclesial communities must strive to reach’. In fact, ‘the elements of this already-given Church exist, joined together in their fullness in the Catholic Church and, without this fullness, in the other communities’. (Congregation for the Doctrine of the Faith. Declaration Dominus Iesus, no. 17, August 6, 2000)

First of all we should call to mind the ‘fullness of grace and truth entrusted to the Catholic Church’ (Unitatis redintegratio 3). In this the Church is a beneficiary of the fact that ‘it was to the apostolic college alone, of which Peter is the head, that we believe that our Lord entrusted all the blessings of the New Covenant, in order to establish on earth the one Body of Christ into which all those should be fully incorporated who belong in any way to the people of God’ (Unitatis redintegratio 3). (International Theological Commission. Select themes of Ecclesiology, Ch. IX, no. 2, October 7, 1985)

With Faith urging us we are forced to believe and to hold the one, holy, Catholic Church and that, apostolic, and we firmly believe and simply confess this (Church) outside which there is no salvation nor remission of sin, the Spouse in the Canticle proclaiming: ‘One is my dove, my perfect one. One she is of her mother, the chosen of her that bore her’ (Ct 6:8); which represents the one mystical body whose head is Christ, of Christ indeed, as God. And in this, ‘one Lord, one faith, one baptism’ (Eph 4:5). Certainly Noah had one ark at the time of the flood, prefiguring one Church which perfect on one cubit had one ruler and guide, namely Noah outside which we read all living things on the earth were destroyed. Moreover this we venerate and this alone, the Lord in the prophet saying: ‘Deliver, 0 God, my soul from the sword; my only one from the hand of the dog’ (Ps 21:21). For in behalf of the soul, that is, in behalf of himself, the head itself and the body he prayed at the same time, which body he called the ‘Only one’ namely, the Church, because of the unity of the spouse, the faith, the sacraments, and the charity of the Church. This is that ‘seamless tunic’ of the Lord (Jn 19:23), which was not cut, but came forth by chance. Therefore, of the one and only Church (there is) one body, one head, not two heads as a monster, namely, Christ and Peter, the Vicar of Christ and the successor of Peter, the Lord Himself saying to Peter: ‘Feed my sheep’ (Jn 21:17). (Denzinger-Hünermann 870-872. Boniface VIII, Bull Unam sanctam, November 18, 1302)

The true Church of Jesus Christ was established by divine authority, and is known by a fourfold mark, which we assert in the Creed must be believed; and each one of these marks so clings to the others that it cannot be separated from them; hence it happens that that Church which truly is, and is called Catholic should at the same time shine with the prerogatives of unity, sanctity, and apostolic succession. Therefore, the Catholic Church alone is conspicuous and perfect in the unity of the whole world and of all nations, particularly in that unity whose beginning, root, and unfailing origin are that supreme authority and ‘higher principality’ of blessed Peter, the prince of the Apostles, and of his successors in the Roman Chair. No other Church is Catholic except the one which, founded on the one Peter, grows into one ‘body compacted and fitly joined together’ (Eph 4:16). (Denzinger-Hünermann 2888. Pius IX, Letter of the Sacred Office to the bishops of England, September 16, 1864)

It is so evident from the clear and frequent testimonies of Holy Writ that the true Church of Jesus Christ is one, that no Christian can dare to deny it. But in judging and determining the nature of this unity many have erred in various ways. (Leo XIII. Encyclical Satis cognitum, no. 4, June 29, 1896)

This becomes even more evident when the purpose of the Divine Founder is considered. For what did Christ, the Lord, ask? What did He wish in regard to the Church founded, or about to be founded? This: to transmit to it the same mission and the same mandate which He had received from the Father, that they should be perpetuated. […] The Church, therefore, is bound to communicate without stint to all men, and to transmit through all ages, the salvation effected by Jesus Christ, and the blessings flowing there from. Wherefore, by the will of its Founder, it is necessary that this Church should be one in all lands and at all times. to justify the existence of more than one Church it would be necessary to go outside this world, and to create a new and unheard – of race of men. (Leo XIII. Encyclical Satis cognitum, no. 4, June 29, 1896)

That the one Church should embrace all men everywhere and at all times was seen and foretold by Isaiah, when looking into the future he saw the appearance of a mountain conspicuous by its all surpassing altitude, which set forth the image of ‘The House of the Lord’ – that is, of the Church, ‘And in the last days the mountain of the House of the Lord shall be prepared on the top of the mountains’ (Is 2:2). But this mountain which towers over all other mountains is one; and the House of the Lord to which all nations shall come to seek the rule of living is also one. ‘And all nations shall flow into it. And many people shall go, and say: Come, and let us go up to the mountain of the Lord, and to the House of the God of Jacob, and He will teach us His ways, and we will walk in His paths’ (Ibid., 2:2-3). (Leo XIII. Encyclical Satis cognitum, no. 4, June 29, 1896)

And to set forth more clearly the unity of the Church, he makes use of the illustration of a living body, the members of which cannot possibly live unless united to the head and drawing from it their vital force. Separated from the head they must of necessity die. ‘The Church,’ he says, ‘cannot be divided into parts by the separation and cutting asunder of its members. What is cut away from the mother cannot live or breathe apart’. What similarity is there between a dead and a living body? (Leo XIII. Encyclical Satis cognitum, no. 5, June 29, 1896)

But mark this well: unless the faithful remain bound together by the same ties of virtue, worship and sacrament, and all hold fast to the same belief, they cannot be perfectly united with the Divine Redeemer, the universal Head, so as to form with Him one visible and living body. ‘A whole faith,’ says Saint Leo, ‘a true faith, is a mighty bulwark. No one can add anything to it, no one can take anything away from it; for unless it is one, it is no faith at all.’ To preserve this unity of faith, all teachers of divine truths—all bishops, that is—must necessarily speak with one mind and one voice. (John XXIII. Encyclical Aeterna Dei sapeientia, no. 40 November 11, 1961)

The Catholic Church is a unique institution in the world; divine and human at the same time, with twenty centuries of existence, however, always young, untiringly persues, through human activity, supernatural ends that easily escape superficial observers. (John XXIII. Address to the Foreign Press in Italy, October 24, 1961)

Connected with the uniqueness of Christ’s salvific mediation is the uniqueness of the Church he founded. The Lord Jesus, in fact, established his Church as a saving reality: as his Body, through which he himself accomplishes salvation in history. Just as there is only one Christ, so his Body is one alone: ‘one, holy, catholic and apostolic Church’ (cf. Symbolum fidei, DS 48). The Second Vatican Council says in this regard: ‘Basing itself on Scripture and Tradition, this holy Council teaches that the Church, a pilgrim on earth, is necessary for salvation’ (Lumen gentium, 14). (John Paul II. Address to the members, consultors and staff of the Congregation for the Doctrine of the Faith, no. 4, January 28, 2000)

It is a mistake, then, to regard the Church as a way of salvation along with those constituted by other religions, which would be complementary to the Church, even if converging with her on the eschatological kingdom of God. Therefore we must reject a certain indifferentist mentality ‘characterized by a religious relativism which leads to the belief that one religion is as good as another’ (cf. Redemptoris missio, no. 36). (John Paul II. Address to the members, consultors and staff of the Congregation for the Doctrine of the Faith, no. 4, January 28, 2000)

Since the Church is one, if the Movements are really gifts of the Holy Spirit, they must, naturally, be inserted into the Ecclesial Community and serve it so that, in patient dialogue with the Pastors, they can be elements in the construction of the Church of today and tomorrow. (Benedict XVI. Address to the members of Communion and Liberation Movement on the 25^th anniversary of its Pontifical Recognition, March 24, 2007)

Heresy is the obstinate denial or obstinate doubt after the reception of baptism of some truth which is to be believed by divine and Catholic faith; apostasy is the total repudiation of the Christian faith; schism is the refusal of submission to the Supreme Pontiff or of communion with the members of the Church subject to him. (Code of Canon Law, Can. 751)

If there arises among you a prophet or a dreamer who promises you a sign or wonder, urging you to follow other gods, whom you have not known, and to serve them: even though the sign or wonder he has foretold you comes to pass, pay no attention to the words of that prophet or that dreamer; for the Lord, your God, is testing you to learn whether you really love him with all your heart and with all your soul. (Deut 13:2-4)

I urge you, brothers, to watch out for those who create dissensions and obstacles, in opposition to the teaching that you learned; avoid them. For such people do not serve our Lord Christ but their own appetites, and by fair and flattering speech they deceive the hearts of the innocent. For while your obedience is known to all, so that I rejoice over you, I want you to be wise as to what is good, and simple as to what is evil. (Rom 16: 17-19)

I am amazed that you are so quickly forsaking the one who called you by (the) grace (of Christ) for a different gospel (not that there is another). But there are some who are disturbing you and wish to pervert the gospel of Christ. (Gal 1: 6-7)

But even if we or an angel from heaven should preach (to you) a gospel other than the one that we preached to you, let that one be accursed! As we have said before, and now I say again, if anyone preaches to you a gospel other than the one that you received, let that one be accursed! (Gal 1:8-9)

Some, by rejecting conscience, have made a shipwreck of their faith, among them Hymenaeus and Alexander, whom I have handed over to Satan to be taught not to blaspheme. (1Tim 1:19-20)

Whoever teaches something different and does not agree with the sound words of our Lord Jesus Christ and the religious teaching is conceited, understanding nothing, and has a morbid disposition for arguments and verbal disputes. From these come envy, rivalry, insults, evil suspicions, and mutual friction among people with corrupted minds, who are deprived of the truth, supposing religion to be a means of gain. Indeed, religion with contentment is a great gain. (1Tim 6:3-6)

Be eager to present yourself as acceptable to God, a workman who causes no disgrace, imparting the word of truth without deviation. Avoid profane, idle talk, for such people will become more and more godless, and their teaching will spread like gangrene. Among them are Hymenaeus and Philetus, who have deviated from the truth by saying that (the) resurrection has already taken place and are upsetting the faith of some. (2Tim 2:15-18)

Just as Jannes and Jambres opposed Moses, so they also oppose the truth – people of depraved mind, unqualified in the faith. But they will not make further progress, for their foolishness will be plain to all, as it was with those two. (1Tim 3:8-9)

For the time will come when people will not tolerate sound doctrine but, following their own desires and insatiable curiosity, will accumulate teachers and will stop listening to the truth and will be diverted to myths. (2Tim 4:3-4)

For there are also many rebels, idle talkers and deceivers, especially the Jewish Christians. It is imperative to silence them, as they are upsetting whole families by teaching for sordid gain what they should not. (Tit 1:10-11)

In the nature of the One, then, is associated in a joint heritage the one Church, which they strive to cut asunder into many sects. Therefore in substance and idea, in origin, in pre-eminence, we say that the ancient and Catholic Church is alone, collecting as it does into the unity of the one faith — which results from the peculiar Testaments, or rather the one Testament in different times by the will of the one God, through one Lord — those already ordained, whom God predestinated, knowing before the foundation of the world that they would be righteous. But the pre-eminence of the Church, as the principle of union, is, in its oneness, in this surpassing all things else, and having nothing like or equal to itself. (Saint Clement of Alexandria. Stromata Book VII, Ch. 17)

But because the Manichæans preach another Christ, and not Him whom the apostles preached, but a false Christ of their own false contrivance, in imitation of whose falsehood they themselves speak lies, though they may perhaps be believed when they are not ashamed to profess to be the followers of a deceiver. (Saint Augustine of Hippo. Reply to Faustus the Manichæan, Book XII, no. 4)

But it will be said, If the words, the sentiments, the promises of Scripture, are appealed to by the Devil and his disciples, of whom some are false apostles, some false prophets and false teachers, and all without exception heretics, what are Catholics and the sons of Mother Church to do? How are they to distinguish truth from falsehood in the sacred Scriptures? They must be very careful to pursue that course which, in the beginning of this Commonitory, we said that holy and learned men had commended to us, that is to say, they must interpret the sacred Canon according to the traditions of the Universal Church and in keeping with the rules of Catholic doctrine, in which Catholic and Universal Church, moreover, they must follow universality, antiquity, consent. (Saint Vincent of Lerins. Commonitory, Ch. 27, no. 70)

This arises from the fact that numbers of them —indeed, we may say all— desire themselves to be teachers, and to break off from the particular heresy in which they have been involved. Forming one set of doctrines out of a totally different system of opinions, and then again others from others, they insist upon teaching something new, declaring themselves the inventors of any sort of opinion which they may have been able to call into existence. (Saint Irenaeus of Lyon. Against Heresies, Book I, Ch. 28, 1)

Those who are called Encratites (self-controlled) preached against marriage, thus setting aside the original creation of God, and indirectly blaming Him who made the male and female for the propagation of the human race. […] A certain man named Tatian first introduced the blasphemy. He was a hearer of Justin’s, and as long as he continued with him he expressed no such views; but after his martyrdom he separated from the Church, and, excited and puffed up by the thought of being a teacher, as if he were superior to others, he composed his own peculiar type of doctrine. […] Others, again, following upon Basilides and Carpocrates, have introduced promiscuous intercourse and a plurality of wives, and are indifferent about eating meats sacrificed to idols, maintaining that God does not greatly regard such matters. But why continue? For it is an impracticable attempt to mention all those who, in one way or another, have fallen away from the truth. (Saint Irenaeus of Lyon. Against Heresies, Book I, Ch. 28, 1-2)

The Church of Christ, therefore, is one and the same forever; those who leave it depart from the will and command of Christ, the Lord – leaving the path of salvation they enter on that of perdition. ‘Whosoever is separated from the Church is united to an adulteress. He has cut himself off from the promises of the Church, and he who leaves the Church of Christ cannot arrive at the rewards of Christ… He who observes not this unity observes not the law of God, holds not the faith of the Father and the Son, clings not to life and salvation’ (S. Cyprianus, De Cath. Eccl. Unitate, n. 6). (Leo XIII. Encyclical Satis cognitum, no. 5, June 29, 1896)

We are to be congratulated when such as these are separated from the Church, lest they should lay waste the doves and sheep of Christ with their cruel and envenomed contagion. Bitterness cannot consist and be associated with sweetness, darkness with light, rain with clearness, battle with peace, barrenness with fertility, drought with springs, storm with tranquility. Let none think that the good can depart from the Church. The wind does not carry away the wheat, nor does the hurricane uproot the tree that is based on a solid root. The light straws are tossed about by the tempest, the feeble trees are overthrown by the onset of the whirlwind. The Apostle John execrates and severely assails these, when he says, ‘They went forth from us, but they were not of us; for if they had been of us, surely they would have continued with us’ (1Jn 2:19). Hence heresies not only have frequently been originated, but continue to be so; while the perverted mind has no peace — while a discordant faithlessness does not maintain unity. (Saint Cyprian of Carthage. On the Unity of the Church, no. 9-10)

And if at any time a part opposes itself to the whole, novelty to antiquity, the dissent of one or a few who are in error to the consent of all or at all events of the great majority of Catholics, then they must prefer the soundness of the whole to the corruption of a part; in which same whole they must prefer the religion of antiquity to the profaneness of novelty; and in antiquity itself in like manner, to the temerity of one or of a very few they must prefer, first of all, the general decrees, if such there be, of a Universal Council, or if there be no such, then, what is next best, they must follow the consentient belief of many and great masters. (Saint Vincent of Lerins. Commonitory, Ch. 27, no. 70)

Surely nothing should be preferable to a Catholic man than that schisms and dissensions among Christians be torn out by the roots and that all Christians be ‘careful to keep the unity of the Spirit in the bond of peace’ (Eph 4:3). But, that the faithful of Christ and the clergy should pray for Christian unity under the leadership of heretics, and, what is worse, according to an intention, polluted and infected as much as possible with heresy, can in no way be tolerated. (Denzinger-Hünermann 2887. Pius IX, Letter of the Sacred Office to the bishops of England, September 16, 1864)

And we know that these sects are not very stable: at any given time, it may be all very well to proclaim prosperity, miraculous healings, etc., but after a while, it becomes clear that life is difficult, that a human God, a God who suffers with us is more convincing, more real, and offers greater help for life. It is also important that we have the structure of the Catholic Church. We do not proclaim a small group that after a certain time becomes isolated and lost, but we enter into this great universal network of catholicity, which is not only trans-temporal, but above all, it is present as a great network of friendship that unites us and also helps us to overcome individualism so as to arrive at this unity in diversity, which is the true promise. (Benedict XVI. Interview during the flight to Africa, March 17, 2009)

In this atmosphere of a rationalism closing in on itself and that regards the model of the sciences as the only model of knowledge, everything else is subjective. Christian life too, of course, becomes a choice that is subjective, hence, arbitrary and no longer the path of life. It therefore naturally becomes difficult to believe, and if it is difficult to believe it is even more difficult to offer one’s life to the Lord to be his servant. […] On the other hand, the sects that present themselves with the certainty of a minimum of faith are growing, and the human being seeks certainty. Thus, the great Churches, especially the great traditional Protestant Churches, are truly finding themselves in a very deep crisis. The sects have the upper hand because they appear with a few simple certainties and say: ‘This suffices’. (Benedict XVI. Address to diocesan clergy of Aosta in the Parish Church at Introd, July 25, 2005)

We have to remember, however, that there are no lack of deviations which gave origin to sects and Gnostic, or pseudo-religious movements, configuring a widespread cultural fashion which finds an echo in ample sectors of society and has influence even within catholic ambiences. For this reason, some of them, in a syncretistic perspective, amalgamate biblical and Christian aspects with others taken from oriental philosophies or religions, magic, and psychological techniques. This expansion of sects and of new religious groups that attract many of the faithful and sow confusion and uncertainty among Catholics is a cause for pastoral concern. (John Paul II. Address to a group of Bishops of the Argentinean Episcopal Conference on their ad limina visit, February 7, 1995)

‘We know that Cornelius, bishop of the most holy Catholic Church, was chosen by God almighty and by Christ our Lord; we confess our error; we have suffered imposture; we have been deceived by treachery and captious loquacity; for although we seemed to have held, as it were, a certain communication with a schismatical and heretical man, nevertheless our heart has always been in the Church; for we are not ignorant that there is one God and that there is one Lord Christ, whom we have confessed, that there is one Holy Spirit and that there ought to be one bishop in the Catholic Church.’ (Denzinger-Hünermann 108. Saint Cornelius. Letter Quantam Solicitudinem to Saint Cyprian, bishop of Carthage, 252)

First of all, the impiety and perversity of Arius and his followers were examined,… and it was unanimously decided to condemn his impious doctrine and the blasphemous utterances by which he expressed himself regarding the Son of God: maintaining in fact that he came from nothing and that prior to his birth he did not exist; he also said that the Son of God, through his free will, had capacity for both good and evil and called him a creature and something made. The holy council anathematized all of this, not wishing even to listen to this impious and insane doctrine or such blasphemous language. (Denzinger-Hünermann 130. Marcellinus, Synodal Letter to the Egyptians)

Know then that already long ago we condemned that profane man Timothy, the disciple of Apollinarius the heretic, along with his godless doctrine. In no way do we believe that his legacy will exercise any influence from now on. (Denzinger-Hünermann 149. Damasus I, Letter to the Eastern Bishops, ca. 378)

All the bishops established in the sacred synod of the Carthaginian Church have decided that whoever says that Adam, the first man, was made mortal, so that, whether he sinned or whether he did not sin, he would die in body, that is he would go out of the body not because of the merit of sin but by reason of the necessity of nature, let him be anathema. (Denzinger-Hünermann 222. Synod of Carthage, May 1, 418)

[The impiety of the Priscillianists] has sunk even into the darkness of paganism, with the result that, through the profane and secret practices of the magical arts and the hollow deceptions of astrologers, they base religious faith and moral laws upon the power of demons and the influence of the stars. But if it were permitted for this to be believed and taught, no reward would be owed to virtues or punishment to vices, and all rules not only of human laws but also of divine ordinances would be dissolved; for it would be impossible for there to be any judgment in regard either to good acts or to bad ones if a fated necessity compelled the movement of the mind in the two directions and if whatever is done by men comes, not from men, but from the stars…With good reason our fathers… took decisive action, so that (this) impious delusion might be driven from the whole Church. (Denzinger-Hünermann 283. Leo I, the Great. Letter Quam laudabiliter to Bishop Turribius of Astorga, July 21, 447)

Your public reproof is public salvation, and your opinion is medicine. From this I also draw the highest remedy, that by blaming past errors I excuse [them], and by healing confession I wash myself. Just so in consequence of the recent statutes of the Council about to be published, I condemn with you that view which states that the work of human obedience does not have to be united with divine grace; which says that after the fall of the first man the free choice of the will was totally destroyed; which states that Christ our Lord and Savior did not incur death for the salvation of all; which states that the foreknowledge of God violently impels man to death, or that they who perish, perish by the will of God; which affirms that whoever sins after baptism which has been legitimately received dies in Adam; which states that some have been condemned to death, others have been predestined to life; which states that from Adam even to Christ none of the nations has been saved unto the coming of Christ through the first grace of God, that is, by the law of nature, and that they lost free will in the first parent; which states that the patriarchs and prophets or every one of the highest saints, even before the times of the redemption, entered into paradise. All these I condemn as impious and replete with sacrileges. (Denzinger-Hünermann 330-339. Synod of Arles, from the letter of submission of the priest Lucidus, 475)

Desiring not to be separated from this hope and faith and following the ordinances of the Fathers, we anathematize all heresies, especially the heretic Nestorius, who at one time was bishop of the city of Constantinople, condemned in the Council of Ephesus by the blessed Celestine, Pope of the City of Rome, and by the venerable man Cyril, high priest of the City of Alexandria. Similarly anathematizing both Eutyches and Dioscorus of Alexandria condemned in the holy Synod of Chalcedon which we follow and embrace, which following the sacred Council of Nicea proclaimed the apostolic faith, we detest both Timothy the parricide, surnamed the Cat, and likewise his disciple and follower in all things, Peter of Alexandria. We condemn, too, and anathematize Acacius, formerly bishop of Constantinople, who was condemned by the Apostolic See, their confederate and follower, or those who remained in the society of their communion, because Acacius justly merited a sentence in condemnation like theirs in whose communion he mingled. No less do we condemn Peter of Antioch with his followers, and the followers of all mentioned above. (Denzinger-Hünermann 364. Saint Hormisdas, Libellus professionis fidei, added to the epistle Inter ea quae to the bishops of Spain, April 2, 517)

It, moreover, anathematizes, execrates, and condemns every heresy that suggests contrary things. And first it condemns Ebion, Cerinthus, Marcion, Paul of Samosata, Photinus, and all similar blasphemers, who, being unable to accept the personal union of humanity with the Word, denied that our Lord Jesus Christ was true God, proclaiming Him pure man, who was called divine man by reason of a greater participation in divine grace, which He had received by merit of a more holy life. It anathematizes also Manichaeus with his followers, who, thinking vainly that the Son of God had assumed not a true but an ephemeral body, entirely do away with the truth of the humanity in Christ. (Denzinger-Hünermann 1339-1340. Council of Florence, from the Bull Cantate Domino, February 4, 1442)

If anyone does not confess that the Word, without detriment to the immutability of his divine nature, was made flesh and that from his very conception in the womb of the Virgin he united, according to hypostasis, the principles of human nature, but says that God the Word was with a preexisting man, so that, as a consequence, one cannot believe that the holy Virgin was in fact the Mother of God, but only that she is said to be such in name, let him be anathema. (Denzinger-Hünermann 416. Constitution Inter innúmeras sollicitudines on the ‘Three Chapters’ to Emperor Justinian, May 14, 553)

Strive with all possible care to make men understand and show forth in their lives what the Catholic Church teaches on government and the duty of obedience. Let the people be frequently urged by your authority and teaching to fly from the forbidden sects, to abhor all conspiracy, to have nothing to do with sedition, and let them understand that they who for God’s sake obey their rulers render a reasonable service and a generous obedience. (Leo XIII. Encyclical Diuturnum illud, no. 27, June 29, 1881)

Hoping that because of your exhortations and your interest in this work the Catholic people shall never permit themselves to be outdone in generosity by non-Catholics who are wont to assist so liberally the propagators of their false beliefs. (Pius XI. Encyclical Rerum Ecclesiae, no. 17, February 28, 1926)

Yet let no one think that all the socialist groups or factions that are not communist have, without exception, recovered their senses to this extent either in fact or in name. For the most part they do not reject the class struggle or the abolition of ownership, but only in some degree modify them. Now if these false principles are modified and to some extent erased from the program, the question arises, or rather is raised without warrant by some, whether the principles of Christian truth cannot perhaps be also modified to some degree and be tempered so as to meet Socialism half-way and, as it were, by a middle course, come to agreement with it. (Pius XI. Encyclical Quadragesimo anno, no. 116, May 15, 1931)

The first question asks if the Second Vatican Council changed the previously held doctrine on the Church.
The question concerns the significance of what Paul VI described in the above mentioned quotation as ‘the new face’ of the Church offered by Vatican II. The response, based on the teaching of John XXIII and Paul VI, is very clear: the Second Vatican Council did not intend to change – and therefore has not changed – the previously held doctrine on the Church. It merely deepened this doctrine and articulated it in a more organic way. This is, in fact, what Paul VI said in his discourse promulgating the Dogmatic Constitution Lumen gentium when he affirmed that the document had not changed traditional doctrine on the Church, but rather ‘that which was assumed, is now explicit; that which was uncertain, is now clarified; that which was meditated upon, discussed and sometimes argued over, is now put together in one clear formulation’ (Paul VI, Discourse – September 21, 1964). There is also a continuity between the doctrine taught by the Council and that of subsequent interventions of the Magisterium which have taken up and deepened this same doctrine, which itself constitutes a development. In this sense, for instance, the Declaration of the Congregation for the Doctrine of the Faith Dominus Iesus merely reaffirmed the conciliar and post-conciliar teachings without adding or taking away anything. In the post-conciliar period, however, and notwithstanding these clear affirmations, the doctrine of Vatican II has been, and continues to be, the object of erroneous interpretations at variance with traditional Catholic doctrine on the nature of the Church: either seeing in it a ‘Copernican revolution’ or else emphasizing some aspects almost to the exclusion of others. In reality the profound intention of the Second Vatican Council was clearly to insert the discourse on the Church within and subordinate to the discourse on God, therefore proposing an ecclesiology which is truly theological. The reception of the teaching of the Council has, however, often obscured this point, relativising it in favor of individual ecclesiological affirmations, and often emphasizing specific words or phrases which encourage a partial and unbalanced understanding of this same conciliar doctrine. (Congregation for the Doctrine of the Faith. Commentary on the document Responses to some questions regarding certain aspects of the doctrine of the Church, June 29, 2007)

The second question asks what is meant by the affirmation that the Church of Christ subsists in the Catholic Church. When G. Philips wrote that the phrase ‘subsistit in’ had caused ‘rivers of ink’ to be spilt, he would probably never have imagined that the discussion would continue for so long or with such intensity as to have provoked the Congregation for the Doctrine of the Faith to publish this present document. This publication, based on the conciliar and postconciliar texts which it cites, reflects the concern of the Congregation to safeguard the unity and unicity of the Church, which would be compromised by the proposal that the Church founded by Christ could have more than one subsistence. If this were the case we would be forced, as the Declaration Mysterium Ecclesiae puts it, to imagine ‘the Church of Christ as the sum total of the Churches or the ecclesial Communities – which are simultaneously differentiated and yet united’, or ‘to think that the Church of Christ no longer exists today concretely and therefore can only be the object of research for the Churches and the communities.’ If this were the case, the Church of Christ would not any longer exist in history, or would exist only in some ideal form emerging either through some future convergence or through the reunification of the diverse sister Churches, to be hoped for and achieved through dialogue. The Notification of the Congregation for the Doctrine of the Faith concerning a book of Leonardo Boff is even more explicit. In response to Boff’s assertion that the one Church of Christ ‘is able to subsist in other Christian Churches’, the Notification states that ‘the Council chose the word ‘subsistit’ specifically to clarify that the true Church has only one ‘subsistence’, while outside her visible boundaries there are only ‘elementa Ecclesiae’ which – being elements of the same Church – tend and lead to the Catholic Church.’ (Congregation for the Doctrine of the Faith. Commentary on the document Responses to some questions regarding certain aspects of the doctrine of the Church, June 29, 2007)

The third question asks why the expression ‘subsistit in’ was used rather than the verb ‘est’. It is precisely this change of terminology in the description of the relationship between the Church of Christ and the Catholic Church which has given rise to the most varied interpretations, above all in the field of ecumenism. In reality, the Council Fathers simply intended to recognise the presence of ecclesial elements proper to the Church of Christ in the non-Catholic Christian communities. It does not follow that the identification of the Church of Christ with the Catholic Church no longer holds, nor that outside the Catholic Church there is a complete absence of ecclesial elements, a ‘churchless void’. What it does mean is that if the expression ‘subsistit in’ is considered in its true context, namely in reference to the Church of Christ ‘constituted and organised in this world as a society… governed by the successor of Peter and by the Bishops in communion with him’, then the change from est to subsistit in takes on no particular theological significance of discontinuity with previously held Catholic doctrine. In fact, precisely because the Church willed by Christ actually continues to exist (subsistit in) in the Catholic Church, this continuity of subsistence implies an essential identity between the Church of Christ and the Catholic Church. The Council wished to teach that we encounter the Church of Jesus Christ as a concrete historical subject in the Catholic Church. The idea, therefore, that subsistence can somehow be multiplied does not express what was intended by the choice of the term ‘subsistit’. In choosing the word ‘subsistit’ the Council intended to express the singularity and non ‘multipliability’ of the Church of Christ: the Church exists as a unique historical reality. Contrary to many unfounded interpretations, therefore, the change from ‘est’ to ‘subsistit’ does not signify that the Catholic Church has ceased to regard herself as the one true Church of Christ. (Congregation for the Doctrine of the Faith, Commentary on the document Responses to some questions regarding certain aspects of the doctrine of the Church, June 29, 2007)

The expression sister Churches occurs often in ecumenical dialogue, above all, in the dialogue between Catholics and Orthodox, and is the object of continuing study by both parties. While there is certainly a legitimate use of this expression, an ambiguous use has become prevalent in contemporary writings on ecumenism. In conformity with the teaching of the Second Vatican Council and the post-conciliar Papal Magisterium, it is therefore appropriate to recall the correct and proper use of this expression. It is helpful to begin with a brief historical outline. […] In fact, in the proper sense, sister Churches are exclusively particular Churches (or groupings of particular Churches; for example, the Patriarchates or Metropolitan provinces) among themselves. It must always be clear, when the expression sister Churches is used in this proper sense, that the one, holy, catholic and apostolic Universal Church is not sister but mother of all the particular Churches. One may also speak of sister Churches, in a proper sense, in reference to particular Catholic and non-catholic Churches; thus the particular Church of Rome can also be called the sister of all other particular Churches. However, as recalled above, one cannot properly say that the Catholic Church is the sister of a particular Church or group of Churches. This is not merely a question of terminology, but above all of respecting a basic truth of the Catholic faith: that of the unicity of the Church of Jesus Christ. In fact, there is but a single Church, and therefore the plural term Churches can refer only to particular Churches. (Congregation for the Doctrine of the Faith, Note on the expression ‘sister churches’, A letter to the Presidents of the Conferences of Bishops, no. 1.10-11, June 30, 2000)