Debates in the Reformed circles of the Church range from petty to vicious to important, and I have no interest in jumping into unnecessary argumentation. But, I think the debate over whether Jesus is eternally, but functionally, subordinate to the Father in the Triune Godhead is an important one. The debate itself is basically over, but its after-effects linger.
That said, I just want to contribute one additional piece of information that is best used in contradiction to the view that Jesus is eternally subordinate. It comes from that pious minister, Wilhelmus à Brakel, who says,
When Christ acknowledges the Father to be greater than He (John 14:28), the reference is not to His divinity, for as such He is equal to the Father (Phil. 2:6) and one with the Father (1 John 5:7). This has reference to His office as Mediator, in respect to which the Father calls Him His Servant (Isa. 53:11)Wilhelmus à Brakel, The Christians Reasonable Service, Vol. 1, p. 174.
This quote is helpful in that it forces us to consider the manner in which God’s decrees relate to His Being, as well as to the relation of the Persons. Does God’s eternal decree to save people through Jesus entail that Jesus is eternally functionally subordinate to the Father? The problem with this concept is that it entails eternal dependency. A subordinate, even a subordinate in only a functional sense, entails dependence. If two CEOs of the same business work with equal power in their offices, but legally CEO #2 must always execute the plans of CEO #1, then CEO #2 must rely upon CEO #1. But in the Godhead there can be no “reliance” of one Person upon the Other. And the decree to be a Mediator does not make the Son functionally subordinate because it does not make the Son eternally dependent. á Brakel later says,
Dependency is a reality in men, but not in God. The Son has life in Himself as the Father has life in Himself (John 5:26). The attribute of eternity excludes all possibility of dependency. In the execution of the covenant of grace each Person operates according to the manner of His existence. Thus, the Father’s operation proceeds from Himself, the Son’s from the Father, and the Holy Spirit’s from the Father and the Son–all of which occur without dependency as this would suggest imperfection.
Functional subordiantion is indeed an argument in favor of dependency, and á Brakel’s argument thoroughly contradicts it. In executing the Covenant, each Person “operates according to the manner of His existence”, i.e. without dependence upon the manner of the other Person’s existence. He reasons later that since the Son is begotten, the Son may only operate as the begotten-One. This does not entail that He is subordinated to the Father, but only explains the mode of His existence. So, the concept of eternal, though functional, subordination puts the cart ahead of the horse. It seems like an unreasonable conflation of God’s immanent decrees with His external acts or extrinsic decrees. While there is obviously a relation between the economic work of God to the objective reality of God, the correspondence is not one-to-one, but of analogy. The Son is not objectively, eternally, subordinated to the Father. Instead, it is best to confess what Paul confessed, that,
Though He was in the form of God, He did not count equality with God a thing to be grasped, but emptied Himself by taking on the form of a servant, being born in the likeness of men.Philippians 2:6-7
In my paraphrase: Though Jesus was everlastingly God, equal in worth and power and dignity to the Father, He did not consider that equality something to be clung to greedily, but He veiled His glorious attributes and took on tangible, actual servant-hood at a particular point in time, namely when He became a human. God did not cease to be God, but willingly veiled His everlasting power by becoming a man. So too, we should humble ourselves for the sake of others.