In the Athanasian Creed, is the Son part of the Father?

In the Athanasian Creed, the three Persons are one God, and the ‘one God’ is the Trinity. The question is, how are the three Persons one God? If Father = Son = Spirit, that would be Modalism, where the Father, Son, and Spirit are three names for the same one Entity. So, I want to assume that Father, Son, and Spirit are not simply three names for the same Entity, but that there are differences between them. The Creed also says that the three Persons differ. For example, the Father begat the Son. So, while the Father has a Son, the Son does not have a Son. Such differences exclude Modalism. The following suggest that the Son and Spirit are part of the Father: - Firstly. the Creed says they are one undivided substance. (“nor dividing the Substance"). It also says that the Father is the Source and Origin of the Son and the Spirit. The ‘undivided substance’, therefore, is the substance of the Father. With the Son begotten and the Spirit proceeding, that Substance remains undivided. This means that the Son and Spirit are part of the Father’s Substance; the Son is part of the Father. - Secondly, that is also what Athanasius taught: > - “In the Father we have the Son: this is a summary of Athanasius’ theology.” (Hanson, p. 426) > - “The Son is in the Father ontologically.” (Hanson, p. 428) > - “Athanasius’ increasing clarity in treating the Son as intrinsic to the Father’s being” (Ayres, p. 113) > - “Athanasius’ argument speaks not of two realities engaged in a common activity, but develops his most basic sense that the Son is > intrinsic to the Father’s being.” (Ayres, p. 114) (Read More ) If the Athanasian Creed is supposed to reflect Athanasius’ theology, which I suspect it does, it would be fair to conclude that the Son and Spirit are part of the Father. - Thirdly, Athanasius was the norm of Western pro-Nicene theology and that theology relied heavily on Tertullian, who also said that the Son is part of the Father. > “The Father is the entire substance, but the Son is a derivation and > portion of the whole.” (In Against Praxeas 9, Tertullian)