The Church is a body, a fact asserted in the Sacred Scriptures. “Christ,” the Apostle said, “is the Head of the Body of the Church.” Her members, the faithful, are indeed the member parts of the Church of which “He is the savior of His Body.” As the Church is a body, there must be an unbroken unity, it members cannot be strewn across the battle field of competing doctrine.
We find that embracing the Church of Jesus Christ, the Catholic Church, we are embracing the Bride of Christ. As there is only One God there is but One bride of Christ; there aren’t multiple Christ’s with a multitude of brides nor is Christ a polygamist with multiple brides. Hence, through the Apostle we hear an absolute truth having only one reality, His Church; not His ‘Churches’.
The bride is the Body of Christ persevering in the darkness of the night. The faithful in “the bride of the incarnate Word”, the Catholic Church remains assured in a divine faith “taught by the Holy Spirit” moving always to a fuller truth as one body in obedience, “as Christ also loved the church, and delivered himself up for it:” [Cf. Ephesians 5:22 sq].
The essence of the Divine Person defines His diminutive parts, the converse is not true, that is the arm of Christ does not define the essence of Christ’s Divinity nor His human nature. As the Catholic Church is mystically the Body of Christ there is a corresponding mystical and hypostatic union between the Person of Christ and the corporate Church. Therefore, ‘Church’ subsists in Christ and her members much the same as the Person Christ subsists in His Divine and human natures. And, as there is One Jesus Christ, there can be only One Mystical Body, the Catholic Church.
The Protestant mindset of multiple bodies adhered by some vague notion of ‘Christian’ creating a Frankenstein Church; an amalgamation of parts sown together forming ‘Christian Church’ with threads of doctrinal anarchy.
Catholics commune in the Real presence of Christ as One Body to which He promises never to abandon. The Church is like “a sign and instrument in her communion “with God and of the unity of the whole human race.” [Lumen Gentium, 1]. Sacred Tradition, Sacred Scripture, the Popes, the Councils of Bishops, along with the Early Church Fathers together speaks of the spiritual need of the Catholic Church. Sacred Scripture alone speaks only to the need to locate, and abide in, the One True Church, the Catholic Church. Yet we hear the second biggest non-Catholic denomination in the United States, the denomination of ‘former’ Catholics apostates who sanctimoniously proclaim themselves victims using a ubiquitous definition of Church.
The Kingdom of God is administered for the good of God. We serve in a Communion of faith, "the faith of the faithful is the faith of the Church, received from the apostles. Further, the ‘faithful’ commune in the Sacraments to become Church and the Church communes with the Saints.
The concept of ‘one size fits all’ religion leads to a dead faith. (Cf. Pope Benedict XVI, Principles of Catholic Theology: building stones for a fundamental theology, 1987) Thus, the Church is not a company of like minded believers joined together by some vagaries of Christ’s Divinity and Christ’s humanity. Consider that God’s word is immutable, never changing, and incorruptible; thus we find “God is Truth” (Cf. St. Thomas Aquinas). Objectivity is the basis of One Divine College that can teaches the disciplines of an irreformable Truth infallibly. Only the Divine can receive and bind others to immutable Truth with an authority that obliges discipline within the body faithful that isn’t rooted in hypocrisy. This Divinity is only One Church, the One Body of Christ; which is Catholic Church under one head, One God, One Christ.
Catholics have one faith in unity with Christ. God’s Truth is affirmed in our faith, as our faith affirms the Church; it is only within her that eternal life can be found. The Catholic Church becomes life in Christ. The Twelve Apostles were commissioned to baptize and teach God’s truth to all nations.
God and Truth are convertible; St. Thomas says, “Whence it follows not only that truth is in Him, but that He is truth itself, and the sovereign and first truth.“ [Summa Prima Q, 15 a5] Consequently there is only one absolute infallible truth. The Psalms also conclude that Truth and God are convertible, “I have chosen the way of truth: thy judgments I have not forgotten.” [Psalm 118:30]. The Church is a Divine institution that is commissioned to teach God’s Divine Truth. As Truth is absolute and immutable there can only be one confessed faith, one doctrine and logically one Church. Christ affirmed only one fold and one shepherd. [Cf. Matthew 12:25, John 10:16, John 17:21-22, Philippians 2:2, etc., etc.], not one fold for each self appointed shepherd. This is a Truth affirmed by the Church’s Sacred Scripture and Sacred Tradition.
There is but one Church, Scripture and history reveals that One Church to be the Catholic Church.