Subsistit in

Subsistit in ("subsists in") is a Latin phrase which appears in Lumen gentium,^[1] the document on the church from the Second Vatican Council of the Catholic Church. Since the council, the reason for use of the term "subsists in" rather than simply "is" has been disputed. Generally, those who see little or no change in church teaching in Vatican II insist on the equivalence of subsistit in and "is". Those who point to a new, ecumenical thrust in Vatican II insist that the term was introduced as a compromise after much discussion, and acknowledges new elements in the council's teaching.

The context of the statement is (emphasis added):^[1]

This Church constituted and organized in the world as a society, subsists in the Catholic Church, which is governed by the successor of Peter and by the Bishops in communion with him, although many elements of sanctification and of truth are found outside of its visible structure. These elements, as gifts belonging to the Church of Christ, are forces impelling toward catholic unity.

— Lumen gentium, 8

This is a debate about externals, the institutional integrity of a church, the fullness of the means of salvation.^[2]