My translation of this document delineating Western Trinitarian and Christological thought:
QVICVMQVE VVLT SALVVS ESSE
Whoever wishes to be saved, it is necessary before all things, that he cling to the Catholic faith: unless someone will have held this [faith] whole and undefiled and away from falseness, he will perish eternally.
Nevertheless, the Catholic faith is this: that we are to worship one God in Trinity, and the Trinity in unity, neither confusing the persons nor dividing the substance. There is one person of the Father, another of the Son, and another of the Holy Spirit: but there is one divinity of the Father, and of the Son, and of the Holy Spirit, the glory equal, the majesty coeternal.
That which the Father is, so is the Son, so also is the Holy Spirit. The Father is uncreated, the Son uncreated, the Holy Spirit uncreated. The Father is immeasurable, the Son immeasurable, the Holy Spirit immeasurable. The Father is eternal, the Son eternal, the Holy Spirit eternal. However, there are not three eternal ones but one eternal, just as there are not three uncreated nor three immeasurable, but one uncreated and one immeasurable.
Similarly the Father is almighty, the Son almighty, the Holy Spirit almighty. However, there are not three almighty ones but one almighty. So the Father is God, the Son is God, the Holy Spirit is God. However, there are not three Gods but one God.
So the Father is Lord, the Son Lord, the Holy Spirit Lord. However, there are not three Lords but one Lord, since, just as we are compelled by Christian truth to confess that one unified person is singly God and Lord, so we are prohibited by the Catholic religion to say that there are three Gods or Lords.
The Father is made from nothing, neither created nor begotten. The Son is from the Father alone: not made, nor created, but begotten. The Holy Spirit is from the Father and the Son: not made, neither created nor begotten but proceeding.
Therefore there is one Father, not three Fathers; one Son, not three Sons; one Holy Spirit, not three Holy Spirits. And in this Trinity nothing is before or after, nothing greater or less, but all three persons are coeternal and coequal to each other.
Thus, as in all things, so now as it was said above, both the unity in Trinity and the Trinity in unity is to be worshipped. Therefore, he who wishes to be saved is to understand thus concerning the Trinity.
But it is necessary to eternal salvation that one also believe faithfully in the incarnation of our Lord Jesus Christ. Therefore, the right faith is that we believe and confess, as our Lord Jesus Christ, Son of God, is God and man.
He is God born before the ages from the substance of the Father; he is also man born in time from the substance of his mother – perfect God, perfect man: of a rational soul and human flesh subsisting.
He is equal to the Father according to his divinity; less than the Father according to his humanity.
Although he is God and man, nevertheless there are not two, but there is one Christ — one, however, not by the conversion of divinity into flesh, but by the assumption of humanity into God. One, moreover, not by confusion of substance but by unityof person.
For just as a rational soul and flesh is one man, so God and man is one Christ.
He suffered for our salvation, he descended to the lower realms, on the third day he rose from the dead. He ascended into the heavens, is seated at the right hand of the Father. Thence he will come to judge the living and the dead, at whose coming all men will rise with their own bodies; and they will be returned reasonably according to their own deeds – those who did good things will go into eternal life; those who did bad into eternal fire.
This is the Catholic faith which, unless someone will have believed faithfully and firmly, he will not be saved.
A note from the BCP:
For the removal of doubts, and to prevent disquietude in the use of the Creed commonly called the Creed of Saint Athanasius, it is solemnly declared:
1. That the Confession of our Christian Faith, commonly called the Creed of Saint Athanasius, does not make any addition to the Faith as contained in holy Scripture, but warns against errors which from time to time have arisen in the Church of Christ.
2. That as holy Scripture in divers places promises life to them that believe, and declares the condemnation of them that believe not, so the Church in this Confession declares the necessity, for all who would be in a state of salvation, of holding fast the Catholic Faith, and the great peril of rejecting the same. Wherefore the warnings in this Confession of Faith are to be understood no otherwise than the like warnings in holy Scripture, for we must receive God’s threatenings, even as his promises, in such wise as they are generally set forth in holy Writ. Moreover, the Church does not herein pronounce judgement on any particular person or persons, God alone being the Judge of all.