What else do you need to know? He is the image of the invisible God, the head…
Who is the image of the invisible God, the first born of every creature; for by him were all things created… and he is before all things,… and he is the head of the body,… for it pleased the Father that in him should all fullness dwell; and having made peace through the blood of his cross, by him to reconcile all things unto himself; by him, I say, whether they be things in earth, or things in heaven. Colossians 1:15-20.
The Bible (given by inspiration of God) speaks about Jesus, what else do you need?
Men (the apostles and all) have witnessed and testified about him, what else do you need?
The Holy Spirit (the greatest Teacher) was sent to teach us all truth, what else do you need?