First, let’s define the term “subsists” before proceeding further:
“
SUBSISTENCE. The existence proper to a whole and uncommunicated substance or reality. Subsistence is that perfection whereby a nature is completed and becomes uncommunicated, that is, whereby it becomes itself and distince from all other beings. Something, therefore, subsists when it has being and operation through itself, not through union with another. Applied to God as the being who exists essentially or by identity within his essence; the being who is completely self-sufficient for existence and activity. Also applied by the Second Vatican Council to the Roman Catholic Church, in which, it is said, subsists the fullness of the Church founded by Christ. (Etym. Latin
subsistentia, self-contained existence;
subsistere, to stay, abide; to stand under.)” (John A. Hardon’s
Modern Catholic Dictionary, p. 523).
Lumen gentium and
Orientalium Ecclesiarum do not signify the Catholic Church has ceased to regard itself as the one true Church of Christ; merely that it recognizes Infinite God is not confined to the finite boundaries of the Church Militant for the contingent salvation of all peoples. The Catholic Church has always acknowledged there exist lesser “elements of sanctification” found in separated Churches and communities outside the visible boundaries of her sacramental system (i.e., this explains why converts from the Orthodox are not re-baptized since their Trinitarian formula is recognized as valid). The Congregation for the Doctrine of the Faith’s Document [of 29 June 2007] on *Responses to Some Questions Regarding Certain Aspects of the Doctrine on the Church *elaborates upon this at some length
vatican.va/roman_curia/congregations/cfaith/documents/rc_con_cfaith_doc_20070629_responsa-quaestiones_en.html ]