Light as radiation comes from being-in-relation. Lk. 9, 28: “Now it came to pass about eight days after these words, that he took Peter, James and John and went up the mountain to pray. And as he prayed, the appearance of his countenance was changed and his raiment became a radiant white.”
Ratzinger: “Thus he (Luke) makes it plain that the Transfiguration only renders visible what is actually taking place in Jesus’ prayer: he is sharing in God’s radiance and hence in the manner in which the true meaning of the Old Testament – and of all history – is being made visible, i.e., revelation. Jesus’ proclamation proceeds from this participation in God’s radiance, God’s glory, which also involves a seeing with the eyes of God – and therefore the unfolding of what was hidden. So Luke also shows the unity of revelation and prayer in the person of Jesus: both are rooted in the mystery of Sonship [i.e. relation to the Father]. Furthermore, according to the Evangelists, the Transfiguration is a kind of anticipation of Resurrection and parousia (cf. Mk. 9, 1)/ For his communication with the Father, which becomes visible in his prayer in the Transfiguration, is the true reason why Jesus could not remain in death and why all history is in his hands. He whom the Father addresses is the Son (cf. Jn. 10, 33-36). But the son cannot die. Thus Luke suggests that the whole of Christology – our speaking of Christ – is nothing other than the interpretation of his prayer: the entire person of Jesus is contained in his prayer.”
Read: Jesus Christ is his prayer as pure ontological relation to the Father.
Hence: Jn. 8, 12: “I am the light of the world” – Mt. 5, 14: “You are the light of the world.” Hence, light as radiation is produced by the conversion away from self. This is the meaning of “attitude” that Francis speaks of to the bishops of CELAM: “As can be appreciated, what is at stake here are attitudes. Pastoral Conversion is chiefly concerned with attitudes and reforming our lives. A change of attitudes is necessarily something ongoing: ‘it is a process,’ and it can only be kept on track with the help of guidance and discernment. It is important always to keep in mind that the compass preventing us from going astray is that of Catholic identity, understood as membership in the Church” (July 28, 2013 – Rio de Janeiro).
Tolkien’s Letter to His Son Christopher on the Light That is His Angel
7-8 November 1944 - 20 Northmoor Road, Oxford
....Your reference to the care of your guardian angel makes me fear that 'he' is being specially needed. I dare say it is so.... It also reminded me of a sudden vision (or perhaps apperception which at once turned itself into pictorial form in my mind) I had not long ago when spending half an hour in St. Gregory's before the Blessed Sacrament when the Quarant' Ore' [40 Hours] was being held there. I perceived or thought of the Light of God and in it suspended one small mote (or millions of motes to only one of which was my small mind directed), glittering white because of the individual ray from the Light which both held and lit it. (Not that there were individual rays issuing from the Light, but the mere existence of the mote and its position in relation to the Light was in itself a line, and the line was Light). And the ray was the Guardian Angel of the mote: not a thing interposed between God and the creature, but God's very attention itself personalized. And I do not mean 'personified,' by a mere figure of speech according to the tendencies of human language, but a real (finite) person. Thinking of it since - for the whole thing was very immediate, not recapturable in clumsy language, certainly not the great sense of joy that accompanied it and the realization that the shining poised mote was myself (or any human person that I might think of with love) - it has occurred to me that (I speak diffidently and have no idea whether such a notion is legitimate: it is at any rate quite separate from the vision of the Light and the poised mote) this is a finite parallel to the Infinite. As the love of the Father and Son (who are infinite and equal) is a Person, so the love and attention of the Light to the Mote is a person (that is both with us and in Heaven): finite but divine: i.e. angelic. Anyway, dearest, I received comfort, part of which took this curious form, which I have (I fear) failed to convey: except that I have with me now a definite awareness of you posed and shining in the Light - though your face (as all our faces) is turned from it. But we might see the glimmer in the faces (and persons as apprehended in love) of others..."