"And this is eternal life, that they know you the only true God, and Jesus Christ whom you have sent." (John 17:3 ESV)
What does it mean to know God?
Here are some excerpts from Herman Bavinck, taken from "The Knowledge of God" from his Selected Shorter Works, and originally published as chapter 2 in Our Reasonable Faith (Magnalia Dei) in 1909.
God is the highest good of man -- that is the testimony of the whole Scriptures.
God gives Himself to His people in order that His people should give themselves to Him.
This declaration of faith on the part of the church is not a scientific doctrine, nor a form of unity that is being repeated, but is rather a confession of a deeply felt reality, and of a conviction of reality that has come up out of experience in life.
God was for them not at all a cold concept, which they then proceeded rationally to analyze, but He was a living, personal force, a reality infinitely more real than the world around them. Indeed, He was to them the one, eternal, worshipful Being. They reckoned with Him in their lives, they lived in His tent, walked as if always before His face, served Him in His courts, and worshiped Him in His sanctuary.
They [biblical writers] did not have to strain for words, for their lips overflowed with what welled up out of their hearts, and the world of man and nature supplied them with figures of speech. God was to them a King, a Lord, a Valiant One, a Leader, a Shepherd, a Savior, a Redeemer, a Helper, a Physician, a Man, and a Father. All their bliss and well-being, their truth and righteousness, their life and mercy, their strength and power, their peace and rest they found in Him. He was a sun and shield to them, a buckler, a light and a fire, a fountain and a well-head, a rock and shelter, a high refuge and a tower, a reward and a shadow, a city and a temple.
Such is the experience of the children of God. It is an experience which they have felt because God presented Himself to them for their enjoyment in the Son of His love. In this sense Christ said that eternal life, that is, the totality of salvation, consists for man in the knowledge of the one, true God and of Jesus Christ whom He sent.
Jesus speaks of a knowledge which is not mere information but is instead a real knowing. ... But real knowing includes an element of personal concern and involvement and an activity of the heart.
The knowledge and the love come together... God is known in proportion to the extent that He is loved.
It is the product not of scientific study and reflection but of a childlike and simple faith.