"The Church, without being exactly co-extensive with the Mystical Body, is not adequately distinct from it. For this reason it is natural that between her and it—as within the Mystical Body itself between the head and the members—there should arise a kind of exchange of idioms: Corpus Christi quod est ecclesia. "I am Jesus whom thou persecutest." [Acts 9:5] "He who beholds the Church", says Gregory of Nyssa, "really beholds Christ.""