The precise metaphysical/ectoplasmic nature of such changes remains mysterious, I'm afraid, but there are some valuable clues in the texts gathered and published by Professor C. S. Lewis in his invaluable edition of The Screwtape Letters, particularly toward the end of the volume.
You mention C. S. Lewis. One of my favourite passages of his comes at the end of his address, The Weight of Glory:
"Meanwhile, the cross comes before the crown and tomorrow is a Monday morning... It may be possible for each to think too much of his own potential glory hereafter; it is hardly possible for him to think too often or too deeply about that of his neighbour. The load, or weight, or burden of my neighbour's glory should be laid daily on my back, a load so heavy that only humility can carry it, and the backs of the proud will be broken. It is a serious thing to live in a society of possible gods and goddesses, to remember that the dullest and most uninteresting person you talk to may one day be a creature which, if you saw it now, you would be strongly tempted to worship, or else a horror and a corruption such as you now meet, if at all, only in a nightmare. All day long we are, in some degree, helping each other to one or other of these destinations. It is in the light of these overwhelming possibilities, it is with awe and circumspection proper to them, that we should conduct all our dealings with one another, all friendships, all loves, all play, all politics. There are no ordinary
Edited by Paloma, 14 March 2013 - 09:16 AM.