John 12:46

(Tr. liv. 4) Whereby it is evident, that He found all in darkness. In which darkness if they wish not to remain, they must believe in the light which is come into the world. He says in one place to His disciples, Ye are the light of the world; but He did not say to them, Ye are come a light into the world, that whosoever believeth on you should not abide in darkness. All saints are lights, but they are so by faith, because they are enlightened by Him, from Whom to withdraw is darkness.

"I am come a light into the world." For since the Father is called by this name everywhere both in the Old Testament and in the New, Christ useth the same name also; therefore Paul also calleth Him, "Brightness" (Heb. i. 3), having learnt to do so from this source. And He showeth here His close relationship with the Father, and that there is no separation between them, if so be that He saith that faith on Him is not on Him, but passeth on to the Father. And He called Himself "light," because He delivereth from error, and dissolveth mental darkness.

When the Savior of the world came, he made the true light shine. But they did not want to gaze on it, nor were they willing to walk by the radiance of his teaching. Consequently, darkness overtook them and demanded a penalty for the wickedness that had preoccupied them. And this [darkness] might be said to have reasonably blinded and hardened them. And, just as it follows that the one who has chosen to walk in the light also knows where he is going, so it follows that the one who has not chosen to walk in the light walks in darkness and travels wretchedly along the road of the blind.… For just as the visible sun shoots out its bright beams in order to enlighten those who have ailing eyes, so also does the spiritual Sun, the Light that has no setting or evening, come to the world and through his divine and ineffable miracles cast the brilliant gleam of his deity far and wide.