Meaning and Importance of this Truth
Did the Second Person of the Trinity only become the Son of God at his incarnation, or was he, from all eternity, the only begotten Son of God?
Through the centuries, various men have fought against the doctrine of the eternal Sonship of Christ, and are doing so today. A clear, biblical defence of the truth is desperately needed.
What is meant by the eternal Sonship of Christ, or the eternal generation of the Son? There is one eternal God, in three Persons: the Father, the Son, and the Holy Spirit. From all eternity this one God has existed in these three Persons. God the Father has always been the Father, God the Son has always been the Son, and God the Holy Spirit has always been the Holy Spirit. Christ did not merely become the Son of God at his incarnation (or, as some imagine, at his resurrection), but he was the only begotten Son of the Father from all eternity; he has always been the Son of the Father by an eternal generation.
There is most certainly a great mystery here. Our finite minds cannot fully comprehend how the divine Son was always the divine Son; how there never was a moment when he was not the divine Son; and yet he was begotten by the Father. Yet this is most emphatically what the Holy Scriptures reveal. The spiritually blind have fought against it, but those who love God’s revealed truth hold firmly to it. Strangely, there are those who reject this doctrine, and yet readily concede that there is a doctrine of a Trinity of Persons within the one Godhead–a truth equally as full of mystery as this. As we shall see, however, the eternal Sonship of Christ is essential to the doctrine of the Trinity itself.