The highest point in the knowledge of Christ is, that He is the Son of God. But, this does not appear to be Paul’s point of emphasis. The point is knowing Christ. Philippians 3:8-11 emphasizes the same point. It reads:
Indeed I count everything as loss because of the surpassing worth of knowing Christ Jesus my Lord. For his sake I have suffered the loss of all things and count them as rubbish, in order that I may gain Christ and be found in him, not having a righteousness of my own that comes from the law, but that which comes through faith in Christ, the righteousness from God that depends on faith — that I may know Him and the power of his resurrection, and may share his sufferings, becoming like him in his death, that by any means possible I may attain the resurrection from the dead (ESV).
The Greek word for “know” is the Greek γνῶσις in verse eight and γινώσκω in verse ten. Though the words are slightly different, both relate to knowledge in general, including knowledge about someone or something, but also intimate and personal knowledge that comes from experience and interaction. It explains the idiomatic meaning of a man “to know” a woman to mean that he has had sexual intercourse with her (Gen. 4:1, 17, 25; Judg. 11:39; 19:25; 1 Sam. 1:19; Matt. 1:25; Luke 1:34). The thought captures the meaning of someone coming to know, learn, perceive, or realize especially through personal experience. Galatians 4:8 uses the Greek word “oida” which carries the idea of an interpersonal relationship. It reads, “However at that time, when you did not know God, you were slaves to those which by nature are not gods. Then, in verse nine, he returns to the word ginosko (Gr. γινώσκω), i.e. “coming to know.” It reads, “But now that you have come to know God, or rather to be known by God, how is it that you turn back again to the weak and worthless elementary principles, to which you want to be enslaved all over again?” John writes his first epistle in which he uses the word, “know” thirty-two times. As it pertains to knowing God, it is clear that John is not talking about a mere acquaintance with God. To know Him is to love Him, to adore Him, to obey Him, and to praise Him.
Knowledge of the Son of God is not something that we hope to experience one day in the future when He returns to take us home. This was something attainable in the lifetime of those first-century Christians to whom Paul wrote just like attaining the unity of the faith.