There’s a common pattern in domestic abuse cases, with the abuser professing his love and apologizing, then losing control and lashing out again, then again professing his love and sorrow, and so forth. In such cases its pretty clear that the external truth – a swinging fist – does not match the love that supposedly exists. On the other hand, when someone professes love and acts in ways that are tender and caring, the external truth – the kind actions – tend to confirm that the love is real.

That’s what the Bible means by being a "witness": It represents using what we know, the truth in front of our noses, to judge the nature of love. In this case, the witness is John, who represents the external, literal meaning of the Bible, and the "light" is divine truth brought to the world by Jesus. So John was re-establishing the Word – the laws and prophets of the Old Testament – so that Jesus could show the perfect love and truth that fill it internally. With the two in harmony, those who were willing would be able to know that Jesus was the Lord, an expression of the ultimate, creative, eternal love.

(References: The Apocalypse Explained 27 [2])

4415. Recently arrived souls, or novitiate spirits - that is to say, people who a few days after death of the body have entered the next life - are utterly amazed at the existence of light in the next life, for they bring with them the uninformed idea that there are no other sources of light than the sun and material flame. Still less do they know of a light which brings light to the understanding, for they have not observed it during their lifetime; and still less that such light provides the capacity to think, and by flowing into forms which exist from the light of the world frames everything seen in the understanding. If those novitiate spirits have been good people they are raised up, for the purpose of their instruction, to heavenly communities, passing from one community to another. They are raised up to these so that they may recognize through actual experience that light exists in the next life, a light that is brighter than that which shines in the world can ever be, and that the amount of light they dwell in there determines the amount of intelligence. Some borne up into spheres of heavenly light have spoken to me from there, confessing that they had never believed in any such thing and that the light of the world in comparison was darkness. From there they also looked through my eyes into the light of the world, which they saw to be nothing other than dark cloud. And they said, doing so with feelings of pity, that such was the darkness in which men dwelt. From what has been said one may also see why in the Word the angels of heaven are called angels of light; also that the Lord is the Light, and consequently the Life, for men, John 1:1-8; 8:12.