What Is Tom Bombadil Doing in the Lord of the Rings?

Fascinating thread.

I've always felt that Bombadil represented things which did not yield to logical interpretation by Enlightenment reasoning; hence him being left completely opaque by Tolkien in his backstory explanations (and generally acting nonsensically within the narrative). This does not exclude the interpretations that he represents a kind of pre-Modern nature spirit and in fact seems to support and synergize with those interpretations. It synergizes particularly well with his immunity to technology as discussed in the replies by @jpgcrowley.