1. Part of the recent controversy over the (alleged) eternal submission of the Son concerns the significance of Trinitarian designations. To what extent should we draw metaphysical inferences from Trinitarian designations? Consider some typical characteristics of fathers:
i) Fathers are physical
ii) Fathers used to be babies
iii) Fathers come into being
iv) Fathers die
v) Fathers have fathers
vi) Fathers have mothers
This should serve to illustrate the hazards of unbridled extrapolations from theological metaphors. Up to a point it's proper to draw inferences from theological metaphors, but there needs to be controls on the exercise. Consider two checks:
i) Study the usage of fatherhood and sonship as theological metaphors in Scripture
ii) Consider how God's transcendent attributes delimit the scope of the metaphor
2. Why does Scripture use "father", "son", and "spirit" to designate the persons of the Trinity?
i) Father and son are interrelated metaphors. Familial metaphors.
I've suggested that Scripture uses sonship to signify representation, which–in turn–involves two related concepts:
This has the added advantage that it dovetails with another theological metaphor: royal succession.
ii) Suppose, for the sake of the argument, that the first two persons of the Trinity both had fatherly characteristics. Even if that were the case, it's antecedently unlikely that Scripture would employ paternal designations for two persons of the Trinity. In a book that combats polytheism, to speak of two fathers in the Godhead would be very confusing. So even if (ex hypothesi), the first two persons of the Trinity were fatherly, we'd expect Scripture to use two different designations.
iii) Nicene Christology tries to draw a parallel between the eternal generation of the Son and the eternal procession of the Spirit. Although that creates a nice symmetry, fatherhood and spiration are not cognate metaphors, unlike fatherhood and generation. The symmetry involves an illicit extension of the familial metaphor to something in a different domain.
iv) Having used familial designations for the first two persons of the Trinity, we might expect Scripture to make consistent use of familial designations for all three persons of the Trinity. Presumably the reason it doesn't is because fatherhood and sonship exhaust the theologically suitable metaphors for the Godhead. Once again, in a book that combats paganism and polytheism, Scripture could hardly designate the third person of the Trinity as "wife" or "mother" or "daughter". That would evoke all the wrong associations.
So, when it comes to the third person of the Trinity, Scripture uses a metaphorical designation that belongs to a different category than the family. Why does Scripture designate the third person of the Trinity as the "Spirit"?
Like fatherhood and sonship, this is a flexible metaphor. The designation signifies at least three things:
i) A spirit is an incorporeal person
ii) The Spirit is the agent of inspiration
As such, "breath" is a natural metaphor for the spoken word. Scripture as divine speech.
iii) Breathing is a vital sign. Expiration is a synonym for death
As such, "breath" is a natural metaphor for the agent of spiritual rebirth or spiritual renewal.
The fact that Scripture employs a theological metaphor to designate the third person of the Trinity that's categorically different from the interrelated theological metaphors employed to designate the first two persons of the Trinity should warn us to be wary about the metaphysical inferences we draw from Trinitarian designations. After all, surely this doesn't mean the third person of the Trinity is a different kind of being than the first two persons of the Trinity.