Then spoke Jesus again unto them, saying,
I am the light of the world: he that follows me shall not walk in darkness, but shall have the light of life.
All Commentaries on John 8:12 Go To John 8
Augustine of Hippo
AD 430
The Manichaeans suppose the sun of the natural world to be our Lord Christ; but the Catholic Church reprobates such a notion for our Lord Christ was not made the sun, but the sun was made by Him: inasmuch as all things were made by Him. And for our sake did He come to be under the sun being the light which made the sun: He hid Himself under the cloud of the flesh, not to obscure, but to temper His light. Speaking then through the cloud of the flesh, the Light unfailing, the Light of wisdom says to men, I am the Light of the world.
He withdraws you however from the eyes of the flesh, to those of the heart, in that He adds, He that follows Me shall not walk in darkness, but shall have the light of life. He thinks it not enough to say shall have light, but adds, of life. These words of our Lord agree with those of the Psalm, In Your light shall wesee light; for with you is the well of life. For bodily uses, light is one thing, and a well another; and a well ministers to the mouth, light to the eyes. With God the light and the wellare the same. He who shines upon you, that you may see Him, the Same flows to you, that you may drink Him. What He promises is put in the future tense; what we ought to do in the present. He that follows Me, He says, shall have; i.e. by faith now, in sight hereafter. The visible sun accompanies you, only if you go westward, whither it go also; and even if you follow it, it will forsake you, at its setting. Your God is every where wholly; He will not fall from you, if you fall not from Him. Darkness is to be feared, not that of the eyes, but that of the mind; and if of the eyes, of the inner not the outer eyes; not those by which white and black, but those by which just and unjust, are discerned.