I may attach a clever intro about Allen Iverson later, but for now let’s get to business.
First, I love Wayne Grudem, Bruce Ware, and Owen Strachan. I do not think they are heretics. They are my brothers in Christ. They have each benefited me greatly. Given how this Tweet-Apocalypse started, I feel like it’s important to keep affirming that (along with my complemetarian convictions).
This is purely an academic-theological point, then, not a personally adversarial one: when Grudem et al use quotes about “subordination in modes of subsistence” within the Godhead ad intra as support for subordination in authority of the Son to the Father ad intra, they are taking “modes of subsistence” to mean something it does not mean. This term is a reference to the eternal relations of origin – that the Father begets the Son, and the Father and Son process the Spirit, eternally. Generation and spiration are references to how each person of the Godhead subsists in the one divine essence – the Father as Unbegotten, the Son as Eternally Begotten, the Spirit as Eternally Processed. A synonym for “modes of subsistence” is taxis, a word that denotes order or primacy within the Godhead. Historically these synonyms are used to refer to the order within the Godhead in relation only to generation and spiration. There is no sense in which these terms historically meant subordination related to authority or submission ad intra. To wit, Gregory of Nyssa in Against Eunomius I.16:
that is what [Eunomius] wants to do, in arguing to show that the order observed in the transmission of the Persons amounts to differences of more and less in dignity and nature. In fact he rules that sequence in point of order is indicative of unlikeness of nature: whence he got this fancy, what necessity compelled him to it, is not clear. Mere numerical rank does not create a different nature: that which we would count in a number remains the same in nature whether we count it or not. Number is a mark only of the mere quantity of things: it does not place second those things only which have an inferior natural value, but it makes the sequence of the numerical objects indicated in accordance with the intention of those who are counting. ‘Paul and Silvanus and Timotheus’ are three persons mentioned according to a particular intention. Does the place of Silvanus, second and after Paul, indicate that he was other than a man? Or is Timothy, because he is third, considered by the writer who so ranks him a different kind of being? Not so. Each is human both before and after this arrangement. Speech, which cannot utter the names of all three at once, mentions each separately according to an order which commends itself, but unites them by the copula, in order that the juncture of the names may show the harmonious action of the three towards one end.
Now, we can all agree that Grudem et al are not dividing the essence or positing ontological subordination. My point in quoting Nyssa at length here is to show that, for him (and for the other pro-Nicenes), number was a matter of relations of order, not of anything else.
Lest someone object that Nyssen only references essence and not authority here, Basil (upon whom Nyssen relied heavily) makes the connection between the two explicit in De Spiritu Sancto 18.44-45:
In delivering the formula of the Father, the Son, and the Holy Ghost, our Lord did not connect the gift with number. He did not say “into First, Second, and Third,” nor yet “into one, two, and three, but He gave us the boon of the knowledge of the faith which leads to salvation, by means of holy names. … For the Son is in the Father and the Father in the Son; since such as is the latter, such is the former, and such as is the former, such is the latter; and herein is the Unity. So that according to the distinction of Persons, both are one and one, and according to the community of Nature, one. How, then, if one and one, are there not two Gods? Because we speak of a king, and of the king’s image, and not of two kings. The majesty is not cloven in two, nor the glory divided. The sovereignty and authority over us is one, and so the doxology ascribed by us is not plural but one; because the honour paid to the image passes on to the prototype.
The Fathers spoke of “number” as another synonym for taxis and “modes of subsistence,” and their point cannot be clearer – it is merely a means to speak of the differences with respect to eternal relations of origin, not differences with respect to authority and submission.
There is of course a fitting relation between the fact that the Son is generated and then is sent by the Father ad extra, but “fitting” does not mean “equal to.” The subordination seen in the incarnation is fitting given the Son’s generation, but the Son’s generation does not imply subordination in authority or submission with respect to authority within the Godhead.
This is what it means when we speak of “modes of subsistence” and “modes of action” that follow on them: the Son is generated, therefore it is fitting that he becomes incarnate. In the first there is subordination with respect only to modes of subsistence; in the latter there is subordination in authority within the economy of redemption.