This core is a composite one and entails the ways in which the relationship between nature and grace are worked out and the Roman Catholic self-understanding of the Church which is the main subject of the system itself. The Roman Catholic system can be seen as emerging from the range of the nature-grace motifs which are allowed to coexist within it and serve to enrich it, and expressing itself in the paramount role of the church which is basically understood in Christological terms as the prolongation of the Incarnation of Jesus Christ (p. 24).
That, of course, is an over-simplified version of “what Roman Catholicism is”. At its heart, the Roman Catholic Church, hierarchy and all, considers itself to be “The Mystical Body of Christ”. You can find that idea in all the most recent Catholic literature out there.
Lumen Gentium states it this way:
