The "Athanasian" Creed is heresy. It wasn't written by Athanasius, who actually had a hand in the Nicene Creed. And it contradicts the Nicene Creed, particularly in making the persons so equal there is no point in there being more than one! There is no room for a Father and Son where the two are co-equal and co-eternal, versus the Nicene Creed's "begotten of the Father before all worlds" which shows non-co-eternality.
Your comment suggests there is no point to a Trinity to begin with if they are all equal, so I'm not sure I really understand it. Also, Aquinas specifically says that all three are co-eternal, even in the begetting of the Son; the Father begets the Son always. https://www.newadvent.org/summa/1036.htm (Article 3, Reply to objection 3) Would be interested in hearing why you have taken this view of the Trinity, and some sources about your comments on the Athanasian Creed. :)
Furthermore, John 1:18 says "No man hath seen God at any time; the only begotten Son, which is in the bosom of the Father, he hath declared him." This is where Nicea got the expression "of one substance with the Father." It means the Son was begotten within the Father, and resides in the Father's essence, is not external. The Father then contains the Son but the Son does not contain the Father, even as John says, the Son is in the Father's bossom not the Father in the Son's bossom. So then when the fake "Athanasian" screed says "The Father is the whole God; the Son is the whole God; the Holy Spirit is the whole God" it is heresy. The Father is the whole God, containing both the personalities of the Son and Holy Spirit within His essence; the reverse is not true. By asserting that each person is the "Whole God" the faker who wrote the "Athanasian" heresy document has become a modalist, for he has only one person, because if the Father is the whole God, the Son is the whole God, and the Spirit is the whole God, then the Father, Son, and Spirit are one person in disguise as three! But if the Father contains withing himself two other persons which he generated in his own essence by a process of turning two co-equal divine attributes into persons, without division from himself, who still reside within his essence, and this all was done before creation, before time, then we have one God who is three persons. And that we have without rejecting either of Jesus' statements "I and the Father are one" nor "the Father is greater than I." Nor does it sound Tritheistic so we must compulsively add "and yet there are not three Gods but only one" which you must add after "person 1 is the whole, person 2 is the whole, and person 3 is the whole, yet there are not 3 wholes" (of course not, because you just flattened the persons into simply Oneness Pentecostalism by asserting each one is the whole and therefore each one is fiction and not real persons but just "hats"). The "Athanasian" heresy document is the Oneness Pentecostal hat theory.
To say the Father begets the Son always is heresy, for Scripture saith "the only begottEN" not "the only always begetting." The begetting is in the past, but in the past before creation, before time. Begotten before the worlds, not still being beget tomorrow! Of course Aquinas is a heretic on this point since he comes after the fake "Athanasians" heresy document corrupted the West with this falsity. The Son is co-eternal with the Father only in his essence, not his personality; because he was as a divine attribute, i.e. the logos, co-eternal with the Father as the Father always had a logos, but that logos was not a person until he begot it to endow it with personality to be the Son. This is what the Nicene fathers taught. What the West invented after Augustine is heresy.
The list of anathemas that went with the Nicene Creed included a specific rejection of the view "there was once when he was not." So the equal co-eternity of God the Father and God the Son was upheld since at least Nicaea, against Arius. It is a little odd to see that you are trying to use that council to reject equal co-eternity, when that council in fact upheld it.
Arius was teaching that God cannot subdivide his substance (or even that God has no substance) so "the Son cannot be any part of the uncreated substance" (a quote of Arius). So to him the Son is a creation, who existed neither in substance nor pwrsonality before being begotten. What "Quicumque Vult is Heresy" is saying on the other hand is that the Son always existed as an impersonal divine attribute of one substance with the Father before being begotten to become a person. So "Quicumque Vult is Heresy" is not subject to the anathema against those who says there was a time when the Son simply did not exist. He is saying he always existed but was not always a person.
The "Athanasian" Creed is heresy. It wasn't written by Athanasius, who actually had a hand in the Nicene Creed. And it contradicts the Nicene Creed, particularly in making the persons so equal there is no point in there being more than one! There is no room for a Father and Son where the two are co-equal and co-eternal, versus the Nicene Creed's "begotten of the Father before all worlds" which shows non-co-eternality.
Your comment suggests there is no point to a Trinity to begin with if they are all equal, so I'm not sure I really understand it. Also, Aquinas specifically says that all three are co-eternal, even in the begetting of the Son; the Father begets the Son always. https://www.newadvent.org/summa/1036.htm (Article 3, Reply to objection 3) Would be interested in hearing why you have taken this view of the Trinity, and some sources about your comments on the Athanasian Creed. :)
Furthermore, John 1:18 says "No man hath seen God at any time; the only begotten Son, which is in the bosom of the Father, he hath declared him." This is where Nicea got the expression "of one substance with the Father." It means the Son was begotten within the Father, and resides in the Father's essence, is not external. The Father then contains the Son but the Son does not contain the Father, even as John says, the Son is in the Father's bossom not the Father in the Son's bossom. So then when the fake "Athanasian" screed says "The Father is the whole God; the Son is the whole God; the Holy Spirit is the whole God" it is heresy. The Father is the whole God, containing both the personalities of the Son and Holy Spirit within His essence; the reverse is not true. By asserting that each person is the "Whole God" the faker who wrote the "Athanasian" heresy document has become a modalist, for he has only one person, because if the Father is the whole God, the Son is the whole God, and the Spirit is the whole God, then the Father, Son, and Spirit are one person in disguise as three! But if the Father contains withing himself two other persons which he generated in his own essence by a process of turning two co-equal divine attributes into persons, without division from himself, who still reside within his essence, and this all was done before creation, before time, then we have one God who is three persons. And that we have without rejecting either of Jesus' statements "I and the Father are one" nor "the Father is greater than I." Nor does it sound Tritheistic so we must compulsively add "and yet there are not three Gods but only one" which you must add after "person 1 is the whole, person 2 is the whole, and person 3 is the whole, yet there are not 3 wholes" (of course not, because you just flattened the persons into simply Oneness Pentecostalism by asserting each one is the whole and therefore each one is fiction and not real persons but just "hats"). The "Athanasian" heresy document is the Oneness Pentecostal hat theory.
To say the Father begets the Son always is heresy, for Scripture saith "the only begottEN" not "the only always begetting." The begetting is in the past, but in the past before creation, before time. Begotten before the worlds, not still being beget tomorrow! Of course Aquinas is a heretic on this point since he comes after the fake "Athanasians" heresy document corrupted the West with this falsity. The Son is co-eternal with the Father only in his essence, not his personality; because he was as a divine attribute, i.e. the logos, co-eternal with the Father as the Father always had a logos, but that logos was not a person until he begot it to endow it with personality to be the Son. This is what the Nicene fathers taught. What the West invented after Augustine is heresy.
The list of anathemas that went with the Nicene Creed included a specific rejection of the view "there was once when he was not." So the equal co-eternity of God the Father and God the Son was upheld since at least Nicaea, against Arius. It is a little odd to see that you are trying to use that council to reject equal co-eternity, when that council in fact upheld it.
Arius was teaching that God cannot subdivide his substance (or even that God has no substance) so "the Son cannot be any part of the uncreated substance" (a quote of Arius). So to him the Son is a creation, who existed neither in substance nor pwrsonality before being begotten. What "Quicumque Vult is Heresy" is saying on the other hand is that the Son always existed as an impersonal divine attribute of one substance with the Father before being begotten to become a person. So "Quicumque Vult is Heresy" is not subject to the anathema against those who says there was a time when the Son simply did not exist. He is saying he always existed but was not always a person.