Mary, the Immaculate Conception, is the full acceptance and embodiment of God's act of love for the world.
"God's act of love for the world, embodied in Christ, is already performed; it is a fully accomplished fact. Now it must become fully accepted as such (in the Holy Spirit). It must become fully accepted and embodied in the Church so that the Church becomes his immaculate bride, without spot or taint, as is already the case in Mary (Sion, Ecclesia, Uxor Agni). The believing Christian, therefore, insofar as he can, must bring his existence into conformity with the range of eternal love revealed in Christ. Just as the commandments (Torah) of the Old Testament were the concrete revelation of promised grace--which men were to follow--so the objective mental outlook of the Church (scripture and dogma) is the objective articulation of grace fully revealed and actualized."
Hans Urs von Balthasar, "Truth and Life" in Dogma: Man as Man and Believer, Concilium Vol. 21, New York: Paulist Press, 1967, 89-90.