Sothenes said:"He that hath the Son hath life; and he that hath not the Son of God hath not life."-1 John 5:12
"This is the true God, and eternal life."-1 John 5:20
My knowledge of God is through the risen Christ. I have not seen Him (in person) but I have believed and this believing has come about by God's grace and the out-pouring of His spirit to me. I am no whit deserving of anything from God, yet He has made known His love to me in no uncertain manner. I am a man of the flesh, but I am also a man of the Spirit who is not handicapped by the indoctrination of the church or those who seek to bind me by telling me how to interpret scripture. God is my teacher.
And we know that the Son of God is come, and hath given us an understanding, that we may know him that is true, and we are in him that is true, even in his Son Jesus Christ. This is the true God, and eternal life.
Paraphrasing:
Jesus has given us understanding that we may know God. And we are in Him (God) and we are even in His son Jesus. This is the true God that Jesus has given us understanding of and eternal life is in Him.