On the History and Significance
of "Subsistit in"
in the Dogmatic Constitution Lumen Gentium
by Br. Alexis Bugnolo
In the proposed text of De Ecclesia there appears the Latin phrase in Chapter I, n. 7 of the document as proposed until September 15, 1964:
Haec igitur Ecclesia vera omnium Mater et Magistra, in hoc mundo ut societas constituta et ordinata est Ecclesia catholica, a Romano Pontifice et Episcopis in eius directa . . .
In the text of Lumen gentium, Chapter I, n. 8 (ll. 19-26) of the document as presented to the Council Fathers on September 15, 1964, the passage is rephrased accordingly:
Haec Ecclesia, in hoc mundo ut societas constituta et ordinata, subsistit in Ecclesia catholica, a sucessore Petri et Episcopis in eius compaginem gubernata (13), licet extra eius compaginem elementa plura sanctificationis et veritatis inveniatur, quae ut dona Ecclesiae Christi propria ad unitatem catholicam impellunt.
Along with the proposed text was included an official explanation of the changes made since the last public session in Nov.-Jan. 1963/4. These relationes included the following official explanation of the change of est to subsistit in:
Quaedam verba mutuantur: loco « est », l. 21, dicitur « subsistit in », ut expressio melius concordet cum affirmatione de elementis ecclesialibus quae alibi adsunt.
The version presented to the Council Fathers was subject, in accord with the rules of the Council, to the processus verbales in which the Council was asked to approve or reject the text as proposed, two days later, on September 17, 1964. Of the 2189 Council Fathers present, 2114 votes placet, 11 non placet, 63 placet iuxta modum, 1 did not vote. In accordance with the rules of the Council, this vote approved Chapter I and made it the official text of the first chapter of Lumen Gentium.
To adequately discuss the significance of the term « subsistit in » in the Dogmatic Constitution Lumen Gentium it is necessary to recall that the presumption of correct interpretation is with the official explanation given for the text at the time prior to its approval.
The official explanation given above is the following:
Certain words are changed: in place of "est", in line 21, there is said "subsistit in", as an expression more harmonious with the affirmation of ecclesial elements which are elsewhere. 
What is to be understood by this brief explanation. To understand this, let us have recourse to a few Latin dictionaries. The meaning of the term est is well understood by all who have studied even elementary Latin: est means "is."  The Latin term in means "in" when used, as it is here, in conjunction with the ablative declension. 
But what does the all important and controversial subsistit mean. Let us take a look at some authoritative Latin dictionaries that were available at the time of the Council. Subsisto means "to exist" ; to "exist, be" ; and finally "existere, esse; etre".  This last is one of the most authoritative Lexicons in the Latin language, compiled by the Abbe Migne himself.
But perhaps this implicit assertion that the usage of subsistere has an equivalence significance as "is" will be to hard to swallow by some who have prejudged the matter. Let us then consider the entire text of the official explanation.
Remember that "ecclesial" both in English and Latin means "church-like." Secondly, it is patent that in non-Catholic communities there are things taken from Catholicism. Therefore the official explanation is saying that the term « subsistere in » expresses the truth that the manner in which the Church of Christ is present in the Catholic Church permits "church-like" elements to be found elsewhere.
For those who find this difficult to understand, let us turn to the standard explanation of classical Catholic metaphysics. There is a fundamental distinction of real being as "substance" and "accidents"  "Accidents" by name and definition are characteristics of a real being that inhere in the substance, and may or may not be essential to it.
Take for example the Blessed Virgin Mary. She is truly, really, and substantially present in Heaven, body and soul. Inasmuch as there are pictures (e.g. Tilma of Our Lady of Guadalupe), statutes, medallions depicting Her on earth, she is present accidentally in these. But her presence there is not real nor substantial. Mary is only in 1 place.
Again "Every finite substance has only one act of existence and only one substantial form"  It follows therefore if any act constitutes a substance in reality, it is the substantial cause of a thing.
Again, subsistere has the etymological meaning of "to stand; to make a stand; to withstand; to come to stand, stop, halt, cease; to stay, remain."  And it is nearly identical with the Latin verb from which substance is derived: substo, "to stand firm". 
Now inasmuch as the idea or form, known as the "Church of Christ", the Mystical Body, is distinct from a substantial reality, one cannot use this similar term (substo) and say that the form of the Church substat in Ecclesia catholica; since properly speaking a substance alone substat. And so, just as one says that the human person subsists in a human being ; so one says that the Church of Christ subsistit in (subsists in) the Catholic Church.
Hence there is no reason derived from the official texts themselves to warrant any misunderstanding of this term in of itself, despite what modernists after the Council may claim.
EFFICACY OF THIS STATEMENT
Since the time of the Council much as been written and said about this obscured Scholastic phrase. One might add that its admission of the appearances of Christianity outside the One True Church, the Catholic Church, has not fostered conversion or union; but lead to widespread misunderstanding, interpreted as it is through the actions of the "ecumenism" promoted since the time of the Council. Hence it would be good for the Magisterium to explain the authentic meaning of this phrase, so as to put an end to its inutility in theological writings and talks on the nature of the Church.
The great weakness of this statement, however, consists in likening the form or idea of the Church of Christ with the personhood of the Church. Strictly speaking a form exists accidentally in a rational mind and substantially in real being. To this extent it is incorrect to say that the "Church of Christ subsists in the Catholic Church", for the Church of Christ in this sense by existing as a substance is the Catholic Church. This teaching of Lumen Gentium is therefore somewhat metaphorical, and hence I believe, not strictly an accurate theological statement.
The danger of this philosophic adversion toward likening the idea of the Church of Christ to a person is to open the doors to deeper misunderstandings of the actual reality of the Church. This is because if the form of the Church is like a person, then it is capable of being united by grace with communities which are outside the physical unity of the Church, just as Christ Himself by grace can be united with human persons outside of Himself.
Moreover it must be admitted that the idea of the Church of Christ is a perfection of form in the Mind of God, eternal and unchanging, and that it is this idea which is the exemplar cause of the Church, but that it is the act of the historic Christ which founds the substantial reality which is the Church and the power of the Holy Ghost, in fidelity to His Mission which builds up and sustains Her. It is thus not an idea that subsists in the Church, but rather the Persons of the Holy Trinity which indwell in Her which maker Her the one, true, and authentic, reality which is the Church of Christ. Since God is not a polygamist nor an adulterer or fornicator, it cannot be but one Church which is the Bride of Christ, the Temple of the Holy Trinity. For this reason it is profoundly dangerous to so describe the Church in any manner that may obscure Her unicity and authenticity among Catholics and non-Catholics. Fortunately, much of the misunderstanding was corrected in certain statements of Dominus Iesus,  which the Congregation for the Doctrine of the Faith published 2 years after the first edition of this essay.
Like many other statements in the documents of the Council this one has not borne good fruit. This is just another example of what Our Lord taught the Apostles when He said, "No one lights a lamp and puts it under a bushel basket". That is, no one having true doctrine expresses it in equivocal or vague statements. Alas, this was and is the fault of the fathers of the Second Vatican Council, and the Church has suffered greatly from it, and more greatly inasmuch as its wayward way with words has become the pastoral norm since the Council. May the Lord have mercy on our pastors and grant them the grace and light to speak the truth simply, directly, unequivocally with charity, so as to save souls. For this is the great work of the Church, and it has been greatly injured by the failure of the Council.
1 Constitutiones Dogmaticae Lumen Gentium Synopsis Historia, a cura di Giuseppe Alberigo e Franca Magistretti, Instituto per le Scienze Religiose, Bologna, 1975, p. 38. De Ecclesia was the original name of the document. This Latin phrase is translated by the author of this essay as, "Therefore this Church, the true Mother and Teacher of all, has been constituted and ordered in this world as a society, the Catholic Church, directed by the Roman Pontiff and the Bishops in his . . ."
2 Acta Synodalia Sacrosancti Concilii Oecumenici Vaticani II, vol. III, Periodus Tertia, Pars I, Sessio publica IV, Congregationes Generales LXXX, Sept. 15, 1964, pp. 167-168. Items in italics are in the original. They are used to indicate words or phrases added since the document was last discussed in public session. This Latin sentence is translated by the author of this essay as : "This Church, in this world constituted and ordered as a society, subsists in the Catholic Church, governed by the successor of Peter and the Bishops in his company (13), though outside his company very many elements of sanctification and truth are found, which as gifts proper to the Church of Christ impell to catholic unity."
3 Ibid., p. 177 . The relationes de singulis numberis (pp. 170 ff) were authored by the theological commission entrusted with preparing the text of the document. No appearance of a E/### (intervention number identifying a Council Fathers submitted comments) indicates that the change was made on the initiative of the commission. In this text quoted above the « » exist in the original.
4 Ibid., p. 68.
5 The translation is that of the author of the essay.
6 Cassell's Latin & English Dictionary, D. P. Simpson, MacMillan Publ. Co., New York. 1987., p. xxii, p. 217 "sum".
7 Ibid., p. 111.
8 Medieval Latin Word-List: From British & Irish Sources, J. H. Baxter, D. Litt, Hon. D.D. & Charles Johnson, M.A., British Academy, London; Oxford Univ. Press, 1950, p. 408. This source cites the first appearance in Latin texts in the British Isles of this term as 1451 A.D.
9 A Glossary of Later Latin to 600 A.D., Alexander Souter, Sometimes Regius Prof. Humanities, Univ. Aberdeed., Oxford Clarendon Press, 1945, p. 396. This source cites Marcus Victorinus as its source for usage.
10 Lexicon Manuale Ad Scriptores Mediae et Infimae Latinitatis: ex glossarius Caroli Dufresne, D. Ducancii, D.P. Carpentarii, Adelungii, et aliorum, by M. L'Abbe Migne, Paris, p. 2130. The words -existere- mean "to exist" and -esse- "to be".
11 Summary of Scholastic Principles, Bernard Wuellner, S.J., Prof. Phil, John Carrol Univ., Loyola Univ. Press, Chicago, 1956, principle 39: "Every real complete being is an individual substance." Also, principle 511: "Every complete being is an individual substance and an agent. (This is sometimes referred to as the principle of substance.)"
12 Ibid., principle 512.
13 Cassell's Latin & English Dictionary, p. 215 "subsistere".
15 The human person is the real, substantial, individual thing (considered as individual) constituted by the union of soul and body at conception as a human being. Not every human being is a human person (e.g. Christ, though a human being, according to His Humanity, is a Divine Person according to His individual identity); every human person is destroyed by the disjunction of soul and body, for in this the human being is also destroyed. In technical philosophic terminology "to exist" signifies only the act of real being, whereas "to subsist" signifies the act of real being as circumscribed by another. For this reason it would not be proper to speak of the human soul as "subsisting in" the human person, since the human person, though constituted as an individual substance by both soul and body, nevertheless can cease to exist without this impairing the existence of its human soul. The human soul has existence in the human person; but not subsistence in virtue of it; it has subsistence in virtue of its own immortal being. It is for this reason that the statement "The Church of Christ subsists in the Catholic Church" excludes the possibility of the existence of "The Church of Christ" outside the Catholic Church in any manner except in that circumscribed by the metaphysical term "accident," which excludes real, substantial, individual being. Hence it is that Lumen gentium speaks of "ecclesial," since what is outside the True Church is only "church-like". This distinction is often repeated in post-conciliar documents, and represents a careful, terminological re-affirmation of the unicity of the Mystical Body, the Catholic Church.
16 H.E. Joseph Cardinal Ratzinger, in a book condemning Leonardo Boff wrote: "....In order to justify it, L. Boff appeals to the constitution Lumen Gentium n.8 of the Second Vatican Council. From the Council's famous statement, Haec ecclesia (sc. unica Christi ecclesia) Catholica subsistit in ecclesia Catholica ( This Church---namely the sole Church of Christ---subsists in the Catholic Church) he derives a thesis which is exactly contrary to the authentic meaning of the council text, for he affirms: 'In fact it (sc. the sole Church of Christ) may also be present in other Christian churches' (p.75). But the Council had chosen the word subsitit--subsists--exactly in order to make it clear that the one sole 'subsistence' of the true Church exists, whereas outside her visible structure only 'elementae ecclesia'--elements of the Church exist: these being elements of the same Church tend and conduct toward the Catholic Church (Lumen gentium 8). The decree on ecumenism expressed the same doctrine (Unitatis redintegratio 3,4) and it was restated in Mysterium Ecclesiae." (U.S. Catholic Conference Documentary Service, April 4, 1985, Vol. 14, No. 42, pp 685, 686). Cf. also the next footnote in this essay.
17 Not the many captious statements, but rather in paragraph 16 C: which reads
The Catholic faithful are required to profess that there is an historical continuity — rooted in the apostolic succession — between the Church founded by Christ and the Catholic Church: “This is the single Church of Christ... which our Saviour, after his resurrection, entrusted to Peter's pastoral care (cf. Jn 21:17), commissioning him and the other Apostles to extend and rule her (cf. Mt 28:18ff.), erected for all ages as ‘the pillar and mainstay of the truth' (1 Tim 3:15). This Church, constituted and organized as a society in the present world, subsists in [subsistit in] the Catholic Church, governed by the Successor of Peter and by the Bishops in communion with him”. With the expression subsistit in, the Second Vatican Council sought to harmonize two doctrinal statements: on the one hand, that the Church of Christ, despite the divisions which exist among Christians, continues to exist fully only in the Catholic Church, and on the other hand, that “outside of her structure, many elements can be found of sanctification and truth”, that is, in those Churches and ecclesial communities which are not yet in full communion with the Catholic Church. But with respect to these, it needs to be stated that “they derive their efficacy from the very fullness of grace and truth entrusted to the Catholic Church”.
Though, as is clear, the novel notion of "partial communion" greatly obscures this. This usage of "communion" as "partial" is a philosophical one, not a spiritual one, since there can be no intentional dissent from any Catholic truth in a person, or community, which is in spiritual communion with Her. Nor can one's membership in the Church, spiritually, be "partial", since what is spiritual is indivisible, and what brings about this communion is indivisible (the profession of the one truth faith, the baptismal character, charity, etc.) This latter error of "degrees of communion" is distinct from that of the scholastic phrase subsistit in; and admittedly it is this latter error, which reinterprets the former in an erroneous sense. But as this essay has had as it purpose the examination of this former term only, this latter question is outside its scope of its discussion.