39 We come next in the order of belief to the Holy Church. We have mentioned above why the Creed does not say here, as in the preceding article, “In the Holy Church.” They, therefore, who were taught above to believe in one God, under the mystery of the Trinity, must believe this also, that there is one holy Church in which there is one faith and one baptism, in which is believed one God the Father, and one Lord Jesus Christ, His Son, and one Holy Ghost. This is that holy Church which is without spot or wrinkle. For many others have gathered together Churches, as Marcion, and Valentinus, and Ebion, and Manichæus, and Arius, and all the other heretics. But those Churches are not without spot or wrinkle of unfaithfulness. And therefore the Prophet said of them, “I hate the Church of the malignants, and I will not sit with the ungodly.” But of this Church which keeps the faith of Christ entire, hear what the Holy Spirit says in the Canticles, “My dove is one; the perfect one of her mother is one.” He then who receives this faith in the Church let him not turn aside in the Council of vanity, and let him not enter in with those who practise iniquity.
For Marcion's assembly is a Council of vanity in that he denies that the Father of Christ is God, the Creator, who by His Son made the world. Ebion's is a Council of vanity since he teaches that, while we believe in Christ, we are withal to observe the circumcision of the flesh, the keeping of the Sabbath, the accustomed sacrifices, and all the other ordinances according to the letter of the Law. Manichæus' is a Council of vanity in regard of his teaching; first in that he calls himself the Paraclete, then that he says that the world was made by an evil God, denies God the Creator, rejects the Old Testament, asserts two natures, one good the other evil, mutually opposing one another, affirms that men's souls are co-eternal with God, that, according to the Pythagoreans, they return through various circles of nativity into cattle and animals and beasts, denies the resurrection of our flesh, maintains that the passion and nativity of the Lord were not in the verity of flesh, but only in appearance. It was the Council of vanity when Paul of Samosata and his successor Photinus afterwards taught, that Christ was not born of the Father before the world, but had His beginning from Mary, and believed not that being God He was born man, but that of man He was made God. It was the Council of vanity when Arius and Eunomius taught as their determinate opinion that the Son of God was not born of the very substance of the Father, but was created out of nothing, and that the Son of God had a beginning, and is inferior to the Father: moreover they affirm that the Holy Ghost is not only inferior to the Son, but is also a ministering Spirit. Theirs also is a Council of vanity who confess indeed that the Son is of the substance of the Father, but distinguish and separate the Holy Spirit, while yet the Saviour shows in the Gospel that the power and Godhead of the Trinity are one and the same, saying, “Baptize all nations in the Name of the Father, and of the Son, and of the Holy Ghost,” and it is plainly impious for man to put asunder what God has joined together. That also is the Council of vanity which a pertinacious and wicked contention formerly gathered together, affirming that Christ assumed human flesh indeed, but not a rational soul withal, since Christ conferred one and the same salvation on the flesh, and the animal soul, and the reason and mind of man. That also is the Council of vanity which Donatus drew together throughout Africa, by charging the Church with traditorship (delivering up the sacred books), and with which Novatus disturbed men's minds by denying the grant of repentance to the lapsed, and condemning second marriages, though contracted possibly of necessity. All of these then avoid as congregations of malignants. Those also, if such there be, who are said to assert that the Son of God does not see or know the Father, as Himself is known and seen by the Father; or that the kingdom of Christ will have an end; or that the flesh will not be raised in the complete restoration of its substance; these also who deny that there will be a just judgment of God in respect of all, and affirm that the devil will be absolved from the punishment of damnation due to him. To all these, I say, let the believer turn a deaf ear. But hold fast by the holy Church, which confesses God the Father Almighty, and His only Son, Jesus Christ our Lord, and the Holy Ghost, of one concordant and harmonious substance, believes that the Son of God was born of the Virgin, suffered for man's salvation, rose again from the dead in the same flesh in which he was born; and, lastly, hopes that He will come the Judge of all, through Whom also both the Forgiveness of Sins and the Resurrection of the Flesh are preached.
Source: Commentary on the Apostles' Creed (New Advent)