Charity can never redound in detriment to faith. Therefore, true union among men can only be found in the one Church of Christ, which He founded for the salvation of all.
Perhaps never in the past have we seen, as we see today, the minds of men so occupied by the desire both of strengthening and of extending to the common welfare of human society that fraternal relationship which binds and unites us together in consequence of our common origin and nature.
For since the nations do not yet fully enjoy the fruits of peace – indeed, rather do old and new disagreements in various places break forth into sedition and civic strife – and since on the other hand many disputes which concern the tranquillity and prosperity of nations cannot be settled without the active concurrence and help of those who rule the States and promote their interests, it is easily understood, and the more so because none now dispute the unity of the human race, why many desire that the various nations, inspired by this universal kinship, should daily be more closely united one to another.
The false doctrine of a common basis
Something very similar to this universal fraternity is aimed at by some, in those matters which concern the New Law promulgated by Christ our Lord.
Convinced that men destitute of all religious sentiment are very rarely to be found, they seem to draw from this belief the hope that the nations, although they differ from one another in religious matters, will without much difficulty come to agree as brethren in professing certain doctrines, which form as it were a common basis of the spiritual life. Accordingly, they frequently organize conventions, meetings and addresses, with large public attendance, and at which all without distinction are invited to join in the discussion: both infidels of every kind, and Christians, even those who have unhappily fallen away from Christ or who with obstinacy and pertinacity deny the divinity of His Person and His mission.
Certainly such attempts can in no way be approved by Catholics, founded as they are on that false theory which considers all religions to be more or less good and praiseworthy, in that all in different ways manifest and signify that sense which is inborn in us all, and by which we are led to God and to the obedient acknowledgment of His dominion.
Truly, those who purport this theory are in error and deceived; moreover, they reject the true religion, distorting its principles and gradually turning aside into naturalism and atheism. From this it clearly follows that those who adhere to these theories and efforts deviate completely from the divinely revealed religion. […]
It is man’s duty to believe Revelation absolutely
There can be no true religion other than that which is founded on the revealed word of God.
This revelation, originating from the beginning and continuing under the Old Law, was perfected by Christ Jesus Himself, with the New Law. Now, if God has spoken – and it is historically certain that He has spoken – it is evident that it is man’s duty to believe God’s revelation absolutely and to obey His commands completely. And, so that we might rightly do both, the Only-begotten Son of God founded His Church on earth, for the glory of God and our own salvation. […]
This Church, after being so wonderfully instituted, could not come to an end or be extinguished upon the removal by death of its Founder and of the Apostles who were the first to propagate it, for to it was given the commandment to lead all men, without distinction of time or place, to eternal salvation: “Going therefore and make disciples of all nations” (Mt 28:19).
In the uninterrupted carrying out of this mission, will any element of strength and efficiency be wanting to the Church, when Christ himself is perpetually present to it, according to His solemn promise: “Behold I am with you all days, even to the consummation of the world” (Mt 28:20)?
It follows then that the Church of Christ not only exists today and always, but is also exactly the same as it was in the time of the Apostles, unless we were to say, which God forbid, either that Christ our Lord could not effect His purpose, or that He erred when He asserted that the gates of hell should never prevail against it (cf. Mt 16:18). […]
This being so, it is manifest that the Apostolic See cannot on any terms take part in such assemblies, nor is it in any way lawful for Catholics either to support or to collaborate in such enterprises; for if they do so they will be giving countenance to a false Christianity, far removed from the one Church of Christ.
Revealed truth is not negotiable
Shall We suffer – which would indeed be utterly iniquitous – that the truth, above all a divinely revealed truth, be made subject to negotiation? For the present case is a question of defending revealed truth.
Jesus Christ sent His Apostles into the whole world to permeate all nations with the Gospel Faith, and, lest they should err, He willed beforehand that they be instructed by the Holy Spirit in all the truth (cf. Jn 16:13). Has then this doctrine of the Apostles completely vanished away, or at any time been obscured, in the Church, whose ruler and defence is God himself? If our Redeemer plainly said that His Gospel was to continue not only during the times of the Apostles, but also in future ages, is it possible that the object of faith become, over time, so obscure and uncertain, that it would be necessary today to tolerate opinions that are even incompatible one with another?
If this were true, we should have to confess that the coming of the Holy Spirit to the Apostles, and the perpetual indwelling of the same Spirit in the Church, and the very preaching of Jesus Christ, have several centuries ago lost all their efficacy and use, to affirm which would be blasphemy. […]
Charity is based on a complete and sincere faith
These pan-Christians who turn their minds to uniting the churches may seem to pursue the noblest of objectives in promoting charity among all Christians. But how is it possible that charity redound in in detriment to faith?
Everyone knows that St. John himself, the Apostle of charity, who seems to reveal in his Gospel the secrets of the Sacred Heart of Jesus, and who never ceased to impress on the memories of his followers the new commandment “Love one another,” altogether forbade any intercourse with those who did not profess the doctrine of Christ in all its purity and entirety: “If any one comes to you and does not bring this doctrine, do not receive him into the house or give him any greeting” (2 Jn 1:10).
For which reason, since charity is based on a complete and sincere faith, the disciples of Christ must be united principally by the bond of one Faith. […]
So, Venerable Brethren, it is clear why this Apostolic See has never allowed its subjects to take part in the assemblies of non-Catholics: for the union of Christians can only be promoted by fostering the return to the one true Church of Christ of those who are separated from it, for in the past they have unhappily left it. To the one true Church of Christ, we say, which is visible to all, and which is to remain, according to the will of its Author, exactly the same as He instituted it for the salvation of all. ◊