John has been honoured to give the world the three great revelations that God is spirit, is light, is love. And this profound saying in some sense includes both the others, inasmuch as light, which to the popular mind is most widely apart from matter, may well stand for the emblem of spirit, and, since to radiate is its inseparable quality, does represent in symbol the delight in imparting Himself, which is the very heart of the declaration that God is love. If, then, we grasp these two thoughts of absolute purity and of self-impartation as the very nature and property of God, John tells us that we grasp the kernel of the Gospel.
And he thinks that men never will grasp them certainly unless a 'message' from God, a definite revelation in historical fact, certifies them. We may hope or doubt, or desire, but we cannot be sure that God is light unless he tells us so by unmistakable act. John knew what act that was--the sending of His only-begotten Son. To the positive statement John, in his usual manner, appends an emphatic negative one: 'Darkness is not in him, no, not in any way.' He is light, all light, only light.
II. With characteristic moral earnestness, John passes at once to the practical effects which the message is meant to have. We are not told what God is simply that we may know, but that, knowing, we may do and be. If He is light, two things will follow in those who are in union with Him--they will walk in light, and they will in His light see their own evil. John deals with these two consequences in verses 6-10--the former in verses 6 and 7; the latter in verses 8-10. The parallelism in the construction of these two sets of verses is striking: