Westminster Confession of Faith Chapter 2 - God the Son
The corollary of the doctrine - the eternal Fatherhood of God - is the doctrine of the eternal Sonship of Jesus Christ. We must seek to do justice to the biblical data, and in particular to the fact that Christ has "much to say of God His Father, from whom as His Son He is in some sense distinct, and with whom He is in some equally true sense one" (Biblical and Theological Studies, p37).
The Confessional teaching is that it is peculiarly the property of the Father to beget, by "active generation" (Berkhof, p91). This does not mean prior existence, nor does it mean that the Son is created, nor does it mean that the Son is in any sense dependent upon the Father, as far as His essential personal qualities and characteristics are concerned. What it does mean is that the Father and the Son have the same nature.
William Cunningham elaborates: The eternal generation of the Son, then, just means the communication from eternity, in some ineffable and mysterious way, of the divine nature and essence by the first to the second person of the Godhead, in virtue of which the relation of proper paternity and proper sonship subsists between them, and is accordingly set before us in Scripture in the only way in which it could be unfolded in language applicable to a human relationship, which is in some respects, though not in all, analogous to it. The proper Sonship of Christ, instead of suggesting any considerations inconsistent with His true divinity, most naturally and immediately suggests His being truly of the same nature and substance with the Father, and equal in power and glory.Historical Theology, Vol. 1, p301
Establishing the Deity of Christ
The doctrine of the Person of Christ is explored more fully by the Confession in its 8th Chapter, Sections 1-2. While God has many sons by adoption, He has only one son by generation
The Bible makes clear that belief in the Sonship of Christ is essential to salvation. John tells us that the Word is written "that ye may believe that Jesus is the Christ, the Son of God; and that believing ye may have life through his name" (John 20:31). The same is stated negatively in his epistle: "Who is a liar but he that denieth that Jesus is the Christ? He is antichrist that denieth the Father and the Son" (1 John 2:22).
The deity of Christ is established on several layers of testimony:
1. The Names Ascribed to Him
He is the WORD, who was in the beginning with God and was God. The Jehovah's Witness New World Translation translates: the Word was a god. What that means is undefined. If Christ is an object of worship, His deity is established. If not, the NWT is promoting idolatry. As the Word, Christ is the revelation of the God who is.
He is the IMAGE of the invisible God. All that is in God is in Him. Christ is the brightness of God's glory, and the express image of His Person (Hebrew 1:3). He was, and is, in the form of God (Philippians 2:5). Any reductionism in our attitude to Christ is enforced upon the Greek text of the Word of God at these points.
He is called GOD explicitly. Thomas addresses him as "My Lord and my God" in John 20:28. Hebrews 1:8 applies the words of Psalm 45 to Him - "Thy throne, O God, is for ever and ever"... There are also numerous references to Christ as the Son of God, the grounds on which the Jews concluded that "by our law he ought to die, because he made himself the Son of God" (John 19:7).
2. The Claims He makes of Himself
Geerhardus Vos, in his brilliant volume The Self-Disclosure of Jesus, demonstrates as "by far the most important seat of testimony Jesus bears to his sonship" the words of Matthew 11:27 - "All things are delivered to me by my Father; and no man knoweth the Son but the Father; neither knoweth any man the Father, but the Son, and he to whomever the Son will reveal Him". The context is the sending out of the 70, and Christ rejoices in the success of the Gospel; in Vos's words, he thanks God "because His own Person is the pivot, the center of the whole transaction" (p.147).
This bespeaks intimacy, closeness, knowledge of a peculiarly deep and personal kind. "The dignity lies far above the sphere of ordinary human acquaintance; it carries with itself a unique mutual cognition between Jesus and God. God knows Him and He knows God with an exclusive knowledge" (Vos, p148).
This is no subordinationism. Christ, as the eternal Son, remains God's equal. Only as the Messianic Servant does He become God's subordinate, officially subordinate while remaining personally equal.
Nor is there adoptionism here. At no point does the Sonship of Christ involve a becoming; Son is what He always is, even when He becomes a servant. He never receives Sonship. It is as Son He comes into the world, and transacts the great work, entering freely into the great engagement which will issue in the redemption of the lost.
The Importance of the Doctrine
There can be no doctrine of salvation that is not rooted and grounded in the glorious person of the Son of God. No merely finite creature could ever save. Salvation is of the Lord, and must be prosecuted by Him. When Jesus is entrusted with the work of salvation, it is an all of grace work, which only a divine person can fully execute.
Only an infinite God could qualify as Mediator, as 'daysman' (cf. Job 9:33), one who could unite in His own Person the two natures of those to be reconciled to each other.
Only a divine Saviour could bear the full penalty due to sin, and render full satisfaction to God's law and justice. The eternal efficacy of the sacrifice of atonement hinges upon the eternal glory of His Person. Otherwise there could be no rationale for an eternal salvation grounded upon the work of a day in the history of this world. Only because in his own body God, in Christ, bore our sins to the tree, is it possible for us to hold on to a salvation that is as efficacious as His own glorious and eternal Person will allow it to be.
A concluding word from Philpot: "The eternal Sonship of Christ is, as it were, the central sum of the New Testament, to remove which is to blot out all light from the sky, and to cast the church into darkness and the shadow of death" (The Eternal Sonship of the Lord Jesus Christ, p63).