Therefore, because He was so man, that the God lay hid in Him, there was sent before Him a great man, by whose testimony He might be found to be more than man. And who is this? “He was a man.” And how could that man speak the truth concerning God? “He was sent by God.” What was he called? “Whose name was John.” Wherefore did he come? “He came for a witness, that he might bear witness concerning the light, that all might believe through him.” What sort of man was he who was to bear witness concerning the light? Something great was that John, vast merit, great grace, great loftiness! Admire, by all means, admire; but as it were a mountain. But a mountain is in darkness unless it be clothed with light. Therefore only admire John that you may hear what follows, “He was not that light;” lest if, when you think the mountain to be the light, you make shipwreck on the mountain, and find not consolation. But what ought you to admire? The mountain as a mountain. But lift yourself up to Him who illuminates the mountain, which for this end was elevated that it might be the first to receive the rays, and make them known to your eyes. Therefore, he was not that light.

Wherefore then did he come? “But that he might bear witness concerning the light.” Why so? “That all might believe through him.” And concerning what light was he to bear witness? “That was the true light.” Wherefore is it added true? Because an enlightened man is also called a light; but the true light is that which enlightens. For even our eyes are called lights; and nevertheless, unless either during the night a lamp is lighted, or during the day the sun goes forth, these lights are open in vain. Thus, therefore, John was a light, but not the true light; because, if not enlightened, he would have been darkness; but, by enlightenment, he became a light. For unless he had been enlightened he would have been darkness, as all those once impious men, to whom, as believers, the apostle said, “You were sometimes darkness.” But now, because they had believed, what?—” “but now are you light,” he says, “in the Lord.” Unless he had added “in the Lord,” we should not have understood. “Light,” he says, “in the Lord:” darkness you were not in the Lord. “For you were sometimes darkness,” where he did not add in the Lord. Therefore, darkness in you, light in the Lord. And thus “he was not that light, but was sent to bear witness of the light.” — On John 1:6-14.