According to the New Testament there is and can be only one Body of Christ, one Bride, one flock, one new Temple, one new Israel, one new People of God. All these images connote unity. It would be out of the question for Christ to have several bodies, several brides, or for there to be several new Temples or new Israels. Jesus, moreover, prayed for that there might be one flock and one shepherd (Jn 10:16) and that his disciples might be one, as he and the Father are one (Jn 17:21). Paul gloried in the fact that Christians, since they know only one Lord, one faith, and one baptism (Eph 4:5), are all members of one another (Rom 12:5). So intimate is this fellowship, he declared, that in Christ there is neither Jew nor Greek, slave nor freeman, male nor female (Gal 3:28). All national and racial differences, all distinctions of sex, age, and social class, pale to insigificane in the light of the transcendent unity of the faithful in Christ. For the Church to be divided, Paul implies, is as impossible for Christ to be divided (1 Co 1:13).
— Avery Cardinal Dulles, Models of the Church (New York: Doubleday, 2002), p. 131