"That which was from the beginning, what we have heard, which we have seen with our own eyes, which we have looked upon and touched with our hands, the life was made manifest and we saw it, and testify to it, and proclaim to you the eternal life which was with the Father and was made manifest to us, that which we have seen and heard we proclaim also to you, so that you may fellowship with us; and our fellowship is with the Father and with his son Jesus Christ. And we are writing this that our joy may be complete." 1 John1:1-4.
John in both his Gospel and his two letters, (Peter also) makes it a point to testify to the fact that they saw Jesus with their own two eyes and that they acknowledge that he is God Incarnate. The primary aspect of Christianity, that is missed by modern man is that we Christians do not follow, what Peter described as " cleverly devised myths," we are not subscribing to a set of principles or to an order of philosophical precepts that we developed as a way of life. Jesus Christ was a real person, who lived in human history. The revelation of the Gospels by those who lived with him, who ate, slept, walked, and witnessed him is clear: Jesus was God. God who became a man. The life we live as followers of Christ is to become like Him. We abide in Him and He abides in us. This is a process by which we are converted from the worldy person to the Godly person. Paul wrote: "Do not be conformed to this world but be transformed by the renewal of your mind, that you may prove what is the will of God, what is good and acceptable and perfect." (we subscribed to be perfect, not that we are perfect)
And also: "I have been crucified with Christ; it is no longer I who live, but Christ who lives in me; and the life I now live in the flesh I live by faith in the Son of God, who loved me and gave himself for me."
This transformation requires our participation in God's grace. It is freely given to us and we are free to accept or reject it. It is an open invitation to the divine life. Modern thinkers cannot or will not understand that this is not on par with anything else man can can ponder or philosophize about. That is precisely why John, and Peter testify to the man Jesus. They were transformed by His love and grace. They witnessed something beyond this world. They witnessed His glory. I personally have witnessed Him in my own conversion, not with my human eyes but with my soul. This is beyond anything I could realize without His grace, and I have spent a great deal of my life seeking and searching, I have pondered much. I will testify that to taste what is the Glory of Jesus Christ, the Living God, is to be changed permanently, and nothing is more beautiful and perfect than Christ working through a fool like me.