I've long ago decided for myself that Tom Bombadil is the very spirit of Arda--Arda in a physical form that can walk, talk, and be like a Kid of Eru in the sense that he's almost looking like them.
"Eldest, that's what I am ... Tom remembers the first raindrop and the first acorn ... He knew the dark under the stars when it was fearless — before the Dark Lord came from Outside."
