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 [15]; 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.[16]
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 idenity); 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 imparing the existence of its human soul. The human soul has existence in the human person; but not subsistance in virtue of it; it has subsistance 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. (Br. Alexis Bugnolo, "The History and Significance of 'Subsistit in'")
Irishman note:
Ping to GBCDOJ on his post explaining how "subsists" is more narrow and more specific than "is" per Cardinal Ratzinger.
Ping.