That statement, therefore, which occurs in the gospel, “That was the true Light, which lighteth every one that cometh into the world,” has this meaning, that no man is illuminated except with that Light of the truth, which is God; so that no person must think that he is enlightened by him whom he listens to as a learner, although that instructor happen to be—I will not say, any great man—but even an angel himself. For the word of truth is applied to man externally by the ministry of a bodily voice, but yet “neither is he that planteth any thing, neither he that watereth; but God that giveth the increase.” Man indeed hears the speaker, be he man or angel, but in order that he may perceive and know that what is said is true, his mind is internally besprinkled with that light which remains for ever, and which shines even in darkness. But just as the sun is not seen by the blind, though they are clothed as it were with its rays, so is the light of truth not understood by the darkness of folly.
Reproduced in full. Translation: Nicene and Post-Nicene Fathers, series 1, vol. 5 (Schaff, 1887), public domain (Public domain).