This is an extremely long post, some of it directly from my ponderings in the old, old Virtual Study Group. questioning the nature of the Light of the Trees and it's a bit rambling. I hesitate to post this, but I guess I may as well. At the very least it should draw some fire from more organised and well-read minds.
I preface by saying that I don't offer this as an interpretation based on any evidence from the text, but simply ruminations and disparate thoughts, specifically I think from a tentative offering by someone else way back when which struck me with great force at the time that perhaps the Light of the trees could be seen as Grace in the Christian sense. Basically, the argument was that to a Christian sensibility, the light of the Trees comes close to being the illumination of Soul by Love.
And then there is the question of the source of the ever-replenishing light that the Trees draw on.
Perhaps the Light can be seen as the manifestation on Arda of an aspect of Eru. This occurred to me because of the nature of the light, which not only has physical presence, but seems to permanently affect those who come into contact with it. For example, when Elwë came upon Melian "out of the darkness he looked at her, and the light of Aman was in her face." Elsewhere in the Silm and LOTR, the elves who had seen the Light and returned to ME are regularly described as having the Light in their eyes--granted that could be a metaphor for enlightenment or wisdom, but I've always read that as a physical difference between the Calaquendi and the other Eldar, for it is immediately discernible.
It puts me strongly in mind of Moses after he sees God's back on Mt Sinai from within the protection of a cleft in the rock. Ex 34:
"And as Moses came down from the mountain bearing the two tablets of the pact Moses was not aware that the skin of his face was radiant since he had spoken with Him . Aaron and all the Israelites saw that the skiin of Moses face was radiant....when Moses finished speaking with them, he put a veil over his face." Now, for me the sense is clearly that the divine glory is overwhelming even when merely reflected. This resonates with the Light of the Trees.
It struck me that the Trees were the creation--or more accurately the realization--of Yavanna, who is the only one of the Ainur described as bringing forth life in Arda in a literal way. The others have been responsible for the realization of elemental things--wind, stars, water, earth & rock--or metaphysical aspects--dreams, sorrow, compassion, exuberance etc. Yavannah brings forth life--the olvar and the kelvar. I put aside Aule's creation of the dwarves, for it seems to me that he did so outside the outlined scheme of the Music albeit Eru ratified his act. So, Yavanna could be seen as midwife, rather than creator of the treees, which is appropriate as she is an earth goddess -- the Light is sprung from the fertility of the earth.
Someone in the VTSG pointed out (and I recall it clearly, as it made sene to me and has affected my reading of the story) that the Two Trees themselves could be seen as symbolic of divine duality: day/night, light/dark, order/chaos, which could be seen either in the pagan or Christian sense.
If the Trees and their Light can be taken for a moment as a manifestation of Eru on Arda then one could say that it was this manifestation which rendered Vallinor the "Blessed Realm", over and above its sanctity as a remnant of Arda Unmarred and the dwelling place of the Ainur. It also makes sense that therefore Melkor would both desire and hate the Light--and the Silmarils also, not just because of their unique beauty, but also because the Light and the Silmarils are a manifestation of what he desires and hates--Godhead.
Tolkien writes "The Light failed; but the Darkness that followed was more than loss of light. In that hour was made a Darkness that seemed not lack but a thing with being of its own: for it was indeed made by malice out of light, and it had power to pierce the eye, and to enter heart and mind, and strangle the very will" This is the description of Unlight.
When Melkor leads Ungoliant to the destruction of the trees (yes I know that happens later), he does two things: first he desecrates that manifestation of Godhead by allowing Ungoliant to devour it and transform it to its opposite "an Unlight, in which things seemed to be no more, and which eyes could not pierce, for it was void"
So what Melkor has done here is representative of what he wishes he could do on a larger scale: to vanquish and usurp Eru's place. And Ungoliant, motivated by Melkor's power 'For with my power that I put into thee thy work was accomplished" desires the same. That is to devour the manifestation of godhead in the Light and transform that to herself. To transform day to night, light to dark, order to chaos, life to death.
The second thing that Melkor does is to claim for himself the final remnants of this manifestation of godhead--eventually to place them in his iron crown and become what? Godhead/Eru in his own mind?
I think this perspective on the Light would have a bearing on Fëanor's creation of the Silmarils.
"For Feanor, being come to his full might, was filled with new thought, or it may be that some shadow of foreknowledge came to him of the doom that drew near..."
There is a strong implication that Feanor's urge to capture the light of the Trees in some way, thus ensuring that this light would live on, was intended--that somehow he knew (whence?) that the Trees would be destroyed--that, in fact, he HAD to somehow save the light of the Trees in some way.
Was Feanor in fact the instrument of Eru in this act? That though he came to feel so possessive of the Silmarils, that original impetus came not necessarily from within him? Perhaps he was given 'divine' inspiration to do so? and his fate was dictated by them--and the fate of Arda and of the Valar "air, earth and water" was wrapped by the Silmarils--for how could it be else, if we are actually talking of the destruction and loss of a manifestation of Eru's godhead within Eru's own creation?
Outrageous proposition but it should stimulate some discussion.
I do believe that for Tolkien the image of Moses on Mt Sinai would have had resonance; and I think there is something in the idea of the usurpation and transformation of the symbol of divine creation to its opposite.
Other thoughts:
The three jewels ended up with Earendil (in the air), and in the depths (land and sea). I thought it might be worth mentioning that those are also the elements associated with the Valar: air (Manwe & Varda) land (Aule and Yavanna) and sea (Ulmo)--Melkor is associated with fire. So is there an oblique association made between the fate of the silmarils and the fate of the Valar (these being emblematic of the fate of Arda, as they are its life and it is theirs)?
I think it is worthwhile differentiating between the craft and art of the eldar--a way of describing elven 'magic' (when Galadriel takes Sam and Frodo to the mirror, she tells Sam that this is 'elven magic' though she does not know what mortals mean by that), which is simply a way of harnessing natural forces through empathetic understanding--and industrialisation or progress (or even science in this context) which Tolkien associates with Morgoth (and later with Sauron and Saruman) which may also be a harnessing of natural forces but definitely not empathetically.