“… and the world may know that thou hast sent me.”
The Prayer of Our Lord before the Passion
In the Gospel of St John, Our Lord prays in terms which present the Church’s unity as a visible motive for belief in him and his Church’s claims:
“Holy Father, keep them in thy name whom thou hast given me: that they may be one, as we also are. […]
“[N]ot for them only do I pray, but for them also who through their word shall believe in me. That they all may be one, as thou, Father, in me, and I in thee; that they also may be one in us: that the world may believe that thou hast sent me.
“And the glory which thou hast given me, I have given to them: that, they may be one, as we also are one. I in them, and thou in me: that they may be made perfect in one: and the world may know that thou hast sent me and hast loved them, as thou hast also loved me.” (Emphasis added)ST JOHN 17.11, 20-23
In his encyclical on the ecumenical movement, Mortalium Animos, Pius XI notes an erroneous interpretation of this prayer, which held “that Christ Jesus merely expressed a desire and prayer, which still lacks its fulfilment.” The ecumenical proponents of this idea held that the sum total of Christian sects constitute the true Church; and that while unity of faith and government might one day exist, for now it could “only be regarded as a mere ideal.” Pius XI calls this a “false opinion” and refutes it.
Against the idea that this prayer remains to be fulfilled, Billot writes the following:
“It is certain that this prayer, which expresses the absolute will of Christ, had to be fulfilled infallibly on all points. […]
“Christ was able to address certain requests to his Father in an absolute manner, in the sense that the request concerned precisely the real obtaining of an end and not only the obtaining of means, the use of which is left to human freedom, which can always fail […].
“[T]his request of Christ could not be deprived of its effect and that it must therefore be considered as a law establishing the necessary properties of which the true Church would inevitably be endowed.
“And, as far as we know, no one has ever denied this point.”
That Christ’s prayers infallibly achieve their effects, when made in an absolute manner (as opposed to a mere conditional wish or “velleity”), is not an unusual idea: for example, it is also taught by St Thomas Aquinas.
Billot provides a very beautiful exegesis of Our Lord’s prayer, and then observes:
“On the point of undergoing his passion, Christ thus acts as intercessor with his Father, in favour of his entire flock, both for the shepherds and for the sheep. And so, if we wish to know what is the principal property with which he wished to clothe his Church forever, we must refer to what he asks of his Father in this solemn circumstance.
“Now, what does he ask here for his Church if not unity?
“‘[T]hat they may be one, as we also are… That they all may be one… that they also may be one in us… that, they may be one, as we also are one… that they may be made perfect in one.’
“Christ could not have insisted more on this point, and expressed himself more explicitly.” (Emphasis added)
Note that Billot calls this unity “the principal property” which Christ wished to give his Church – and which he wished to give her perpetually.
Some take this to mean a unity of communion, or even as a mere sentimental fraternity. Some in turn reduce a true concept of unity of communion and government into a merely verbal profession, devoid of reality.
But, without excluding unity of communion, Billot places the emphasis on the unity of faith:
“[I]t is absolutely obvious that when he asks that those who believe in him may be one, Christ is referring to the unity that must be achieved between believers considered as such, and he is therefore thinking above all of the unity of faith of which Saint Paul speaks: ‘One Lord, one faith, one baptism. One God and Father of all.’”
In passing, let’s note that this text of St Paul – “one Lord, one faith, one baptism” – also corresponds to the definition of who is a member of the Church: namely, those who are baptised, profess the faith and are submissive to the Church’s hierarchy.
When we return to the idea above, that this prayer, “which expresses the absolute will of Christ, had to be fulfilled infallibly on all points,” we are left with this conclusion stated explicitly by Billot:
“[The unity of faith] is not provisional but definitive, which must last until the consummation of the age.”
And what, according to Christ himself, is to be the purpose of this perpetual, miraculous unity of faith?
As mentioned, this unity of faith is to serve – along with the unity of communion and government – as a perpetual motive of credibility in Christ’s divine mission and the identity of his true Church.
“[T]hat the world may believe that thou hast sent me […] and the world may know that thou hast sent me and hast loved them.”ST JOHN 17
Unity as a Note of the Church
Vatican I teaches that God endowed the Church “with clear notes to the end that she might be recognised by all as the guardian and teacher of the revealed word.” The Council continues, linking these “clear notes” to the four marks of unity, holiness, catholicity and apostolicity. These notes are so striking, the Council teaches, that by them, the Church herself is made into “a kind of great and perpetual motive of credibility and an incontrovertible evidence of her own divine mission.”
“[V]isibility is the visibility of believability from the four marks which we discussed earlier, by which it is clear that we should believe by faith that this is the only legitimate and genuine religion out of all the religious societies in the world.”
He writes that this visible note of unity is a necessary property of the Church, and one of the means by which she is made visible, knowable, and distinguishable from false sects:
“[T]he threefold unity which Christ has established in the true and legitimate Church cannot fail to appear in full view. […] Christ requires this unity to be a sign of his mission, a note of the true Church […] Not only is this unity a visible and manifest fact, but it cannot coincide in a false Church […] This unity must also have the value of a perpetual proof, to attest Christ’s mission to the world.
“Now, this sign, by which the Father wishes to testify to the very special love with which he surrounds the Church, is reserved for the true Church. And the sign that attests the truth of Christ’s mission cannot be identified with the characteristics that would be found both in false sects and in the legitimate spouse of the Incarnate Word.”
As an example of how this note was viewed, consider the words of M.J. Rhodes in his 1870 work The Visible Unity of the Church, published with episcopal approval:
“Though they may be utter strangers to each other in the flesh, and divided in temporal position as far as men can be divided from their fellow-men, there will be found one and the self-same faith, one and the self-same rule of morals, the self-same sacraments, and the self-same belief respecting those sacraments; there will be found but one mind, one heart, and one voice, as regards all the doctrines and commandments of the Church.
“This is unity, and it is divine; it is no mere human coincidence or contrivance. The finger of God is here, reversing the confusion of Babel.
“It is the unity of God’s one Church throughout the universal globe; and it has been her unity through more than eighteen centuries and a half. It is a matter to be looked to, and a test to be applied, for the absence of such unity denotes the absence of God.”
Billot argues that this unity is not only a necessary property identifying the true Church, but also a miraculous and divine indication of her divine mission.
Unity outside the Church?
In contrast with the Church’s unity, Billot considers apparent instances of unity of faith outside the true Church, arguing (for example) that such are the fruit of enforcement by a civil authority, and limited to the territories of those authorities.
He gives several examples of oaths required of Eastern Orthodox hierarchs and councils, which affirm that they were established by the power of the Tsar, and that their outcomes would be executed “according to the good will of his Imperial Majesty.”
But naturally, while the Tsar might be able to secure unity within his realm, he cannot secure it elsewhere. Billot compares such “parasitic unities” to the unity of the true Roman Church:
“These are all parasitic unities, which seek their foundation in the unity of the race or of the civil society. There is a unity of faith and communion, whose foundation is not of this world, a unity which transcends the limits of a region or an empire, which rises far above the divisions of race, far above the multiplicity of political societies, and which always escapes their vicissitudes.”
When we consider that this unity of faith, arising joyfully and peacefully, achieved without force of arms or other means, pertaining to doctrines far above our minds, and sometimes requiring sacrifices which seem appalling to our fallen human nature, we can see why Billot judges that “it is by definition a seal that confirms the testimony of this Church.” He concludes:
“It will also be understood that this unity is absolutely singular, unique, that it is outside and above all the laws that are observed elsewhere and that it results in a moral miracle that only a special intervention of God can sufficiently explain.”
It should be obvious that there is some disconnect between the points explained here and the apparent facts of our current situation. Today, it is difficult to mount an apologetic argument based on the Church’s visible unity of faith. This issue is addressed here.
But when it comes to the four marks or notes of the Church, unity seems to be the first and most fundamental.
This is because, aside from being a note of the Church, unity is a sort of condition for “being” anything at all – as we have discussed in the original essay from which this piece was taken.
Tradivox Catechism Review
Part I: How can we find the teaching of the universal ordinary magisterium?
Part II: What do the catechisms tell us about heretics and the Church?
Part III: How is the Church “visibly united in faith,” according to Cardinal Billot?
Part IV: Why is it essential that the Church is visibly united in faith?
Part V: What sort of heresy results in being outside the Church?
Part VI: What is the difference between an excommunicate and an open heretic?
Obj. I: Are we obliged to believe every person who calls himself a Catholic?
Obj. II: Should mistaken Catholics be called “material heretics”?
Obj. III: What is the state of a Catholic who submits to a false magisterium?
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 Pius XI, Mortalium Animos, 1928, n. 7: https://www.papalencyclicals.net/pius11/p11morta.htm
 Louis Cardinal Billot, Tractatus de Ecclesia Christi, Tomus Prior, Prati ex Officina Libraria Giachetti, Filii et soc, 1909, p 146. Translated with DeepL from the French translation by l L’Abbé Jean-Michel Gleize SSPX, published as L’Église I – Sa divine institution et ses notes, Courrier de Rome, Versailles, 2009, n. 208.
 “[W]hat we will in accordance with the movement of sensuality, or even of the simple will, which is considered as nature is willed not absolutely but conditionally [secundum quid] – that is, provided no obstacle be discovered by reason’s deliberation. Wherefore such a will should rather be called a “velleity” than an absolute will; because one would will [vellet] if there were no obstacle. Wherefore, according to the will of reason, Christ willed nothing but what He knew God to will. Wherefore every absolute will of Christ, even human, was fulfilled, because it was in conformity with God; and consequently His every prayer was fulfilled.” St Thomas Aquinas, Summa Theologica (and for UK readers), III Q21 A4.
 Billot 156, Gleize n. 225.
 Billot 156, Gleize n. 225.
 Billot 157, Gleize n. 225.
 Vatican I, Chapter 3 on Faith. https://www.papalencyclicals.net/councils/ecum20.htm
 “[T]he church herself by reason of her astonishing propagation, her outstanding holiness and her inexhaustible fertility in every kind of goodness, by her catholic unity and her unconquerable stability, is a kind of great and perpetual motive of credibility and an incontrovertible evidence of her own divine mission.” Ibid.
 Billot 281-2, as translated by Fr Julian Larrabee.
 Billot 282, as translated by Fr Julian Larrabee.
 Billot 159, Gleize n. 228.
 M.J. Rhodes, The Visible Unity of the Catholic Church Maintained against Opposite Theories Vol I, Longmans, Green, and Co., London, 1870, p 35. Available at: https://archive.org/details/visibleunityofca01rhod/page/34/mode/2up?view=theater
 Billot 167, Gleize n. 241
 Billot 170, Gleize n. 243
 Billot 217, Gleize n. 244