Why is “unity of faith” so crucial for making the Church visible, according to Cardinal Billot?

“The branch cannot bear fruit of itself, unless it abide in the vine.”


In Part III, I explained the following matters:

  • Reasons for following Louis Cardinal Billot in matters of ecclesiology
  • Unity of the Church in faith, communion and government
  • Unity of faith – particularly in an external profession – “is the most important aspect of the note of unity”, according to Billot
  • The role of the Church’s magisterium in securing unity of faith
  • What does and doesn’t break this unity of faith
  • How one “professes the faith”, and what constitutes a departure from this profession

In this part, we will consider the reason stated by Our Lord for bestowing the note of unity on his Church, especially in relation to her visibility and credibility – and we will see why unity is so fundamental to the Church’s very existence.

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?

Image: Photo by Boudewijn Boer on Unsplash

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 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.”[1] 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.”[2] 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.”[3]

The infallibility of Christ’s prayers, 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.[4]

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.”[5] (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.’”[6]

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.”[7]

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.”[8] The Council continues, linking these “clear notes” to the four marks of unity, holiness, catholicity and apostolicity.[9] 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.”[10]

As we have already seen, this unity of faith is intimately linked to the visibility of the Church. Billot expresses the same doctrine, linking the four marks to the Church’s visibility:

“[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.”[11]

Billot observes that “all theologians agree unanimously [in the links between visibility, the four marks and the hierarchy] as in a most firm dogma.”[12]

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.”[13]

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.”[14]

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.”[15]

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.”[16]

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.”[17] 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.”[18]

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.

Continues below:

Unity and being

In analogical terms, unity is essential for making something to be what it is.

Insofar as unity is reduced or lost, being itself is also reduced or lost. To follow the analogy used by Our Lord in the same set of discourses in the Gospel of St John, and developed along these lines by St Thomas More – let us consider the example of a vine.

Our Lord tells us that he is the vine, and we are the branches – and that apart from him, we cannot bear any fruit, or indeed do anything. This is rightly understood in terms of the life of grace in our souls, or the impossibility of salvation outside the Church. But let’s abstract from salvation and consider it in more fundamental terms, in relation to the being of the vine.

A branch broken off of a vine is separated from the unity of the vine, considered as a particular being. The branch has become a different thing to the vine. While life and unity continues in the original vine’s being, the branch is now a separate thing – even if it can be somehow grafted back onto the vine. Incidentally, the branch is on its way to yet more disunity through decomposition.[19]

If the vine itself were to lose its unity progressively (for instance, by being slowly broken into pieces), it would eventually come to lose its being altogether, and itself cease to be a living vine.

With regards to the Church, which is a multitude of men united as a society, this unity of faith is a fundamental constituent of her unity and her very being as a single body.

Those who separate themselves from this unity and being, cease to be a part of the body.

Separation from unity of government also leads a man out of the Church. But let’s look more closely at this. Vatican I teaches that Christ instituted the papacy as the “permanent principle” and “visible foundation” of the “unity of faith and communion” amongst the clergy and the faithful.[20] To return to the catechisms which inspired these essays, Fr Frassinetti writes:

“Following the authority of all the Holy Fathers, all Catholics are agreed that the origin and centre of this unity is the Roman Pontiff […] Take away this centre of unity, and they would be so many separate churches, and no longer one Church.”[21]

Therefore, the papacy and unity of government are the foundation of the unities of faith and charity. But in another sense, as we saw in the previous part, unity of faith and charity are more fundamental, because they are the ends to which unity of government is ordered.

And of faith and charity, it is well known that while true faith can exist without charity, true charity cannot exist without faith. In other words, unity of faith is a prerequisite for a unity of charity.

If – though impossible – the Church herself were to cease being united in faith, she would cease to be one body: in fact, she would cease to be, altogether. But just as it would be false to say that the living vine and a separated branch still constitute one vine, so too would it be false to say that the Church and those who separate themselves from her unity still constitute one body. They cannot constitute one body. Billot explains, by comparing the notes of unity and sanctity:

“The holiness of the members we are talking about here concerns individuals directly – and it is indirectly, through these individuals, that holiness can be attributed to the society whose visible principles and mediations contribute to produce this life of grace.

“Unity, however, deals immediately with the collectivity itself, from which it removes division in the profession of faith. Furthermore, the wicked in the Church do not prevent it from containing saints as well, who show it to be true. But if heretics were in the Church, they would formally remove the indivisibility of the society which is of the very definition of unity.”[22]

Van Noort makes the same point in the form of a series of questions:

“If these purely material heretics [N.B.: this refers to those such as Anglicans in good faith – not Catholics in error, for reasons discussed elsewhere] were considered members of the Catholic Church in the strict sense of the term, how would one ever locate the “Catholic Church’? How would the Church be one body? How would it profess one faith? Where would be its visibility? Where its unity?

“For these and other reasons we find it difficult to see any intrinsic probability to the opinion which would allow for public heretics, in good faith, remaining members of the Church.”[23]

In a sense, this is like the “No True Scotsman” fallacy – but while this is a fallacy when applied to Scotsmen, the Church herself teaches that a man ceases to be a Catholic, by definition, by the very fact of his open and clear rejection of the profession of faith.

Complete destruction by division is possible for a real vine, but it is impossible for the Church. Even if whole swathes separate themselves from her[24] and left her much smaller than before, she would still remain what she is: a visible body, united in faith. This would be so, even if she were to be obscured by these masses of open, ex-Catholics who had not been declared as such and expelled by authority.

In any case, in such a circumstance, there must remain the original and true Church, distinct from those who have separated themselves from her.

But even though her unity in faith cannot be lost, and the Church’s being cannot be destroyed, this analogy shows how fundamental the note of unity, especially in faith, is to the Church.[25]

Application to membership and a preliminary conclusion

It should now be becoming clear why it is necessary, by definition, for a person to profess the faith in order to be a member of the Church. For the same reasons, it is necessary that one avoid all acts, words and omissions which are incompatible with this profession of faith. These reasons also show that loss of membership is not a punishment for openly and clearly rejecting the faith: but rather the logical consequence of such a rejection – or, it is that rejection considered from another angle.

In many cases, it is not our business whether a given man has or has not lost membership of the Church: we are not required to go around checking the Catholic credentials of our fellow Mass-attendees. But the situation could be different when it pertains to a supposed member of the hierarchy claiming jurisdiction over us; and perhaps it could be different when it comes to choosing a spouse, teachers for our children, and so on. Of course, there is no pretence here of “declaring” someone to be outside the Church, or of removing them from the Church by our private judgment: this is nothing more than a cognitive recognition of the facts, binding only those of us who are aware of them.

As I mentioned before, it would be false to say that mere mistakes put someone outside the Church. There must be some positive reason to conclude that such things are not mistakes, but true departures from the faith.

But while we all want to give everyone as much benefit of the doubt as is possible, some persons make clear that they are not mistaken, ignorant, or under pressure. Rather, they make it clear that they know what they are doing in departing from the united profession of faith – even if they still claim to be Catholics.

(For more on this, see the objections – to be published in due course).

Further, none of us are required to engage in mental acrobatics. There are some cases of clear and certain departures from the Faith, in the face of which a reasonable man cannot continue to assume the best, or draw any conclusion other than that the person has indeed departed from the Faith.

And what a reasonable man cannot conclude, he certainly cannot be obliged to conclude by some bizarre legal fiction.

To return to St Robert Bellarmine’s words:

“[M]en are not bound to, or cannot scrutinize hearts; but when they see someone acting in a heretical way, they simply judge that he is a heretic, and they condemn him as a heretic.”[26]

And so we have arrived at the case of heretics – those who are not members of the Church, because of their open departure from both the profession of faith and Church’s rule of faith.

They will be the subject of the next part.

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?

See here for the books in the series:

Tradivox Catechism Series – Titles Available (click to expand)

Tradivox I – Three shorter catechisms. (UK readers)

  • Bishop Edmund Bonner – An Honest Godley Instruction. A foundational text written by a bishop who repented under Queen Mary, returned to the Catholic Church and died a confessor under Elizabeth I (1556)
  • Fr Laurence Vaux – A Catechisme of Christian Doctrine (1567)
  • Fr Diego de Ledesma – The Christian Doctrine (1573)

Tradivox II – Three seventeenth-century catechisms. (UK readers)

  • St Robert Bellarmine SJ – A Shorte Catechisme. This consists mostly of restored woodcuts. (1614)
  • Fr Henry Turberville – The Douay Catechism, or An Abridgement of the Christian Doctrine. Very polemically ordered towards catechising Catholics against Protestantism, with many Scripture references and details on the Mass. (1649)
  • Fr Thomas Vincent Sadler – The Childes Catechism. Written for parents. (1678)

Tradivox III – three texts by Bishop Richard Challoner, reviser of the Douay-Rheims Bible and Vicar Apostolic of London during a period of oppressive penal laws. (UK readers)

  • An Abridgement of Christian Doctrine. A synopsis of the Douay Catechism. (1759)
  • The Catholic Christian Instructed. A longer, very annotated work with a lot of focus on worship and the sacraments. (1737)
  • The Grounds of Catholick Doctrine. A simple Q&A catechism based on the Tridentine Profession of Faith (1752)

Tradivox IV: Three significant Irish catechisms, comparable to the Penny or Baltimore Catechisms (UK readers)

  • The Most Rev. Dr James Butler’s Catechism. Approved for national use by all of the Irish bishops, serving Irish Catholics for 150 years at home and in Canada and the USA. (1775)
  • The Catechism Ordered by the National Synod of Maynooth. (1884)
  • The Shorter Catechism Extracted [from the above]. (1891)

Tradivox V: Two by Irish priests in the 1700s. (UK readers)

  • Fr Andrew Donlevy – The Catechism, or Christian Doctrine, By Way of Question and Answer. The oldest major Irish catechetical manuscript. (1742)
  • Fr Thomas Burke OP – A Catechism Moral and Controversial. Written for more advanced audiences, with practical and apologetic notes. (1752)

Tradivox VI: Aquinas, Pecham, and Pagula (UK readers).

  • St Thomas Aquinas – The Catechetical Instructions. An arrangement of other Opuscula in catechetical form. (ca. 1260)
  • Archbishop John Pecham (of Canterbury) – Ignorantia Sacerdotum. Product of the Council of Lambeth. (1281)
  • Quinque Verba – pocket manual to “remedy the ignorance of simple priests.” (1300)
  • William of Pagula – Oculus Sacerdotis – a chapter, frequently excerpted and circulated at the time, from Pagula’s large guide for priests. (1320)

Tradivox VII: The Catechism of the Council of Trent (UK readers)

Tradivox VIII: Pope St Pius X and Frassinetti (UK readers)

Tradivox IX: St Peter Canisius (UK readers)

Tradivox X: Gaume (UK readers) – Jan 2023

Other texts have not been confirmed, but the following are mentioned on the website. They may be intended for publication, or just for the online database.

  • Doulye – A Brief Instruction. (1604)
  • Perry – A Full Course of Instructions for the Use of Catechists.(1847)
  • Fr F.X. Weninger SJ – Manual of the Catholic Doctrine (1867)
  • Baltimore Catechism (1891)
  • Thomas J. O’Brien – An Advanced Catechism of Catholic Faith and Practice (1902)
  • Deharbe’s Large Catechism (1921)
  • Bishop Hay – Abridgement of Christian Doctrine (1800)


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[1] Pius XI, Mortalium Animos, 1928,  n. 7: https://www.papalencyclicals.net/pius11/p11morta.htm

[2] Ibid.

[3] 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.

[4] “[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.

[5] Billot 156, Gleize n. 225.

[6] Billot 156, Gleize n. 225.

[7] Billot 157, Gleize n. 225.

[8] Vatican I, Chapter 3 on Faith. https://www.papalencyclicals.net/councils/ecum20.htm

[9] “[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.

[10] Ibid.

[11] Billot 281-2, as translated by Fr Julian Larrabee.

[12] Billot 282, as translated by Fr Julian Larrabee.

[13] Billot 159, Gleize n. 228.

[14] 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

[15] Billot 167, Gleize n. 241

[16] Billot 170, Gleize n. 243

[17] Billot 217, Gleize n. 244

[18] Billot 217, Gleize n. 244

[19] St Thomas More: “[S]ince only the church of Christ is the vine that Christ spoke of in the Gospel, that he takes for his mystical body, and since every branch cut off from the tree loses its vital nourishment, we must needs well know that all these branches of heretics fallen from the Church, the vine of Christ’s mystical body, no matter how fresh and green they may seem, are yet actually but witherlings that shall shrivel and dry up and be able to serve for nothing but the fire.” Dialogue Concerning Heresies, rendered by Mary Gottschalk, Scepter Press, New York NY, 2006 pp 238

[20] In full: “In order, then, that the episcopal office should be one and undivided and that, by the union of the clergy, the whole multitude of believers should be held together in the unity of faith and communion, he set blessed Peter over the rest of the apostles and instituted in him the permanent principle of both unities and their visible foundation.” Vatican I, Pastor Aeternus, Session 4, 18 July 1870. Available at https://www.papalencyclicals.net/councils/ecum20.htm

[21] Giuseppe Frassinetti, A Dogmatic Catechism, trans. Oblate Fathers of St Charles., in Tradivox Vol. Tradivox VIII (and for UK readers) Sophia Institute Press, Manchester NH, 2022, Q.17, p 21.

[22] Billot 296, translated by Fr Julian Larrabee. The first paragraph is based more closely on the rendering in Cardinal Louis Billot SJ, L’Église II – Sa constitution intime, trans. L’Abbé Jean-Michel Gleize SSPX, Courrier de Rome, 2009, n. 430.

[23] Mgr G. Van Noort, Dogmatic Theology Volume II: Christ’s Church (6th edition), 1957, trans. Castelot & Murphy), 242, n. 153. And see here for UK readers.

[24] ““[E]ven if some nations fall away, yet just as however many boughs may fall from a tree, even if // more fall than are left on it, they still create no doubt as to which is the original tree even if each of them is planted again in another place and grows bigger than the trunk it first came from – just so, when we see and well know that all the companies and sects of heretics are they that are cut off, and that the Church is the trunk that they all came out from.” St Thomas More 238

[25] This analogy is developed at length by St Thomas More, giving an interesting witness to the late medieval doctrine on the matter, in Dialogue Concerning Heresies, rendered by Mary Gottschalk, Scepter Press, New York NY, 2006 pp 224-239

[26] St Robert Bellarmine, Controversies of the Christian Religion, trans. Fr Kenneth Baker SJ, Keep the Faith Press, USA, 2016, in ‘The Third General Controversy,’ on the power of the Roman Pontiff in spiritual matters, p 983

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