Tom Bombadil

[davem]

Over on another forum (LotR Plaza) there's a long discussion on TB (currently 12 pages long). The recently auctioned letter which contains the following

The letter continues with a detailed discussion of The Lord of the Rings, considering Mroczkowski's suggestion as to 'the simultaneity of different planes of reality touching one another ... part of the deeply felt idea that I had ... Beyond that too I feel that no construction of the human mind, whether in imagination or the highest philosophy, can contain within its own "englobement" all that there is ... There is always something left over that demands a different or longer construction to "explain" it ... This is like a "play", in which ... there are noises that do not belong, chinks in the scenery', discussing in particular the status of Tom Bombadil in this respect.

has been discussed & Charles Noad (Tolkien expert who proof read most of HoM-e for Christopher Tolkien) who got to see the whole letter at the auction passed on the following report:

Here Tolkien uses the analogy of a theatrical performance, where as well as the play that is being performed, there are chinks in the scenery which give glimpses of another different world outside - that of the producer and stagehands (and the author!). TB does not belong to the main pattern of the Legendarium, as can be deduced from the fact that the Ring has no effect on him whatsoever - he is outside the problems of power that involve the other characters. Tolkien says that he was tempted to 'tinker' with him to bring him into line, but (most unusually for Tolkien) he resisted that temptation.

So, direct from the horse's mouth, as 'twere, we have a clear statement that Tom is 'external' to the world of Middle-earth, & that Tolkien specifically avoided the temptation to integrate him into the Legendarium. So, the short answer is that Tom 'is' - he is himself: not Eru, or one of the Valar, or an Elf, or anything else.