One of the most natural mistakes commonly made with regard to God’s nature is in the assertion that the Logos became God’s Son at the time of his human birth. This is a natural mistake because human beings find it easy to grant a state of affairs that they can explain from experience. In the context of human experience, nothing is more understandable than sonship through physical birth. One may even find some scriptural justification in a hasty reading of some well-known passages. For example, an angel announced to Joseph that Mary was pregnant by the power of God’s Holy Spirit, and that she would bring forth a son. The angel added that he "shall be called the Son of the Highest" (Luke 1:32). If he shall be called the Son of God, then perhaps his Sonship is connected with his human birth.
The proper beginning place for studying this subject is not the analysis of human sonship, but the fact that Christ was the Son of God during his earthly ministry. This is believed and granted by both sides – by those who think that he has eternally been the Son, and by those who believe that he became the Son through his human birth. With that as a common starting point, the New Testament can be used to shed further light on the question.
In John 8:58, Christ said, "Before Abraham was, I am." The speaker here was the Son of God, and he was saying that he was in existence prior to Abraham’s birth. The present tense "I am" is as abrupt in Greek as it is in English. It is intended to avoid "I was" and "I will be." John was making the point that the Son of God exists before Abraham.
The present-tense expression occurs in other passages of John’s Gospel – see, for example, 8:24 ("that I am," not "that I am he"), 6:20 ("I am," not merely "It is I"), 18:6, etc. In each instance, it was the Son of God who was speaking. It follows that his Sonship is not assumed to start with the incarnation or his human birth.
"Came forth from the Father"
In light of his existence before Abraham was even born, Jesus made statements that can be understood in only one way. In John 16, he says that he "came out from God" (verse 27) and that he "came forth from the Father" (verse 28). The phrase "came forth from the Father" says that the relationship of Father and Son existed before Christ became man. The Son of God, who existed before Abraham was born, came out of God (or came forth from the Father). In so far as he came out of God, he was God, and in so far as he came out of the Father, he was the Son. From the standpoint of both descriptions of his procession, he was the Son of God.
One cannot argue that the expression "came forth from the Father" means to convey the thought that he "came forth from the mother (Mary)." This would be incorrect because the expression "came forth from the Father" is also worded "came out of God" – and Mary was not God.
How this is possible
Hebrews 1:3 says that the Son is "the brightness of his glory." The literal translation of the word for brightness (apaugasma) is reflected radiance. This description of the Son should be closely analyzed. The word apaugasma consists of the preposition apo (from) and auge (bright light, as of the dawn). Perhaps an illustration can serve to show this point. At dawn, one sees the reflected radiance of the sun even before the sun is visible. This announces that the Son of God has a source. He is, by his very nature (as the Son of God), generated by the Father, just as the radiance at dawn is generated by the sun. He is the result of the Father’s radiating glory – what is generated by the Father. This description is in terms of a divine Source and a divine Outcome, or a divine Generator and a divine Generated. Whatever the wording, the meaning is a divine Father and a divine Son. In this sense, the Son had glory with the Father before the world was – because he was the reflected radiance of the Father. As the brightness of the dawn is constantly being generated by the sun, so the Son is constantly generated by the Father.
The sun cannot be what it is without its radiance, neither is the sun’s radiance possible without the sun. Similarly, the Father cannot be without the Son or the Son without the Father. (This is the meaning of hypostasis.) Of course, the same is true of the Holy Spirit; but the issue, at present, is the status of the Son of God before his human birth.
Before the human birth
The Son of God was the brightness of God’s glory (Hebrews 1:3). This was the glory that he had with the Father "before the world was" (John 17:5), before Abraham was even born (John 8:58). As God, he had timeless existence, which is expressible in terms like "I am" (without past or future). As the Son of God, he was sent to be born of a woman and to be under the law (Galatians 4:4), but neither his human birth nor his being under the law was the source of his Sonship (he was already the Son of God). This sending out is described, in the New Testament, as coming "out of God" and as coming "forth. from the Father," because he was already the Son of God. It is the eternal coming forth from the Father that makes him the Son of God – not the fact that he assumed the nature of man.
What difference the point makes
To believe that Jesus became the Son of God by virtue of his human birth denies his divine status. It suggests that the child in Mary’s womb had come about in the manner known to man – that a new being was generated. In other words, it denies pre-existence. This point is worth dwelling on because the only meaning of "son by physical birth" is "a new human being without pre-existence."
People who have asserted the wrong view have not meant to deny the Son’s preexistence. At the same time, intention is one thing, the formulation of an explanation and the language in which the doctrine is couched is another. The formulation and the doctrine may entail a direction that is not intended.
The truth is that Jesus was the Son of God by virtue of his divinity, not by virtue of his humanity.