To me this is one of the most interesting topics/discussions in the whole
Tolkien universe. Reading about how
Bombadil puts on
the ring and is completely unaffected and how he sees
Frodo when he puts on the ring and enters the "other" world (call it what you may) is one of my favorite parts in all of Tolkien's writings.
Based off what Tolkien himself has said (I wish I had the quote but I do not),
Tom Bombadil CANNOT be any already known character in the Tolkien universe. Tolkien specifically shot down the theory that Bombadil was
Eru and he went out of his way to say that every fictional universe has to have characters that are not fully understood by anyone, and that is exactly what Bombadil is. If Tolkien had intended for Bombadil to be anyone in particular (such as
Aule for example) he would have said so; it is not Tolkien's style to say Bombadil could not be understood and then secretly leave clues for readers to "figure out" who he is (be he Aule or anyone else).
This is not to say I found your theory uninteresting, Illuin, I very much enjoyed the post

.
Based on the "laws" of Tolkien's universe, it seems that Bombadil was just one of the many unnamed
Maia. This could explain his resistance to the ring, as he was the only Maia to have come in contact with it. (Keep in mind that although the
Istari were indeed Maia, they were Maia in altered forms. They were limited in their powers by the 'mortalesque' bodies they were bound to, and they were never revealed in their true power and majesty due to the limitations assigned to them. Perhaps
Olorin would have been unaffected by the ring even when
Gandalf saw it as a temptation) Tolkien says in
the Silmarillion that there were many
Maiar (unlike the limited and small number of
Valar); it is not at all hard to believe that one of them settled down in ME, even if Tolkien never explicitly mentioned it.
This would also explain how Bombadil could see Frodo when he put on the ring. Gandalf describes in the chapter "Many Meetings" how those who have lived in
Aman live both in the invisible world and the visible world at the same time. If Bombadil were just an "earthly spirit" or an incarnation of nature, it seems to me that he would not have this quality. We can reasonably conclude that he had spent some time in
Valinor at one time. Knowing he is not an
elf or mortal, who else has ever lived in Aman? The
Ainur of course, and due to my above reasoning of why he can't be a known character (thus ruling out all Valar), he must be a Maia!
As far as the issue of why Bombadil was not counted among
the wise and why the wise never took council with him (it would be logical they would try to use a Maia's help if there was one in ME), he just simply did not care! It's as Prince of Cats already said, he ignored the
wars of mortals and
elves (much like the
ents) because there are always wars and there always will be, but Ea had existed always. I loosely liken him to
Radagast, that although by no means was
evil or bad, he did not get involved with the worries of the wise because he was enamored by the forest and nature and peaceful things. Can you blame the guy? He certainly led a much more care-free lifestyle.
