From Letter #144
I would not, however, have left him in, if he did not have some kind of function. I might put it this way. The story is cast in terms of a good side, and a bad side, beauty against ruthless ugliness, tyranny against kingship, moderated freedom with consent against compulsion that has long lost any object save mere power, and so on; but both sides in some degree, conservative or destructive, want a measure of control, and if you have, as it were taken a vow of poverty, renounced control, and take your delight in things for themselves without reference to yourself, watching, observing, and to some extent knowing, then the questions of the rights and wrongs of power and control might become utterly meaningless to you, and the means of power and control quite valueless.`
Ultimately only the victory of the West will allow Bombadil to continue, or even to survive. Nothing would be left for him in the world of Sauron.
But many have found him an odd or indeed discordant ingredient. In historical fact I put him in because I had already 'invented' him independently and wanted an 'adventure' on the way. But I kept him in, and as he was, because he represents certain things otherwise left out. I do not mean him to be an allegory -- or I should not have given him so particular, individual, and ridiculous a name -- but 'allegory' is the only mode of exhibiting certain functions: he is then an 'allegory', or an exemplar, a particular embodying of pure (real) natural science: the spirit that desires knowledge of other things, their history and nature, because they are 'other' and wholly independent of the inquiring mind, a spirit coeval with the knowledge...Also T.B. exhibits another point in his attitude to the ring, and its failure to affect him. You must concentrate on some part, probably relatively small, for the World (Universe), whether to tell a tale, however long, or to learn anything however fundamental -- and therefore much will from that 'point of view' be left out, distorted on the circumference, or seem a discordant oddity. The power of the Ring over all concerned, even the Wizards or Emissaries, is not a delusion -- but it is not the whole picture, even of the state and content of that part of the Universe.
And even in a mythical Age there must be some enigmas, as there always are. Tom Bombadil is one (intentionally).
Using the following definitions
:Enigma is a mystery, something that seems to be unrelated or out of place, but isn't.
An anomaly is a mystery, something that is unrelated, out of place.
Tolkien has told us that Tom Bombadil is an enigma and does have a place in LOTR. Screen and stage writers appear to have treated Tom Bombadil more of an anomaly in LOTR.
So was the encounter with Tom Bombadil out of place in LOTR?
If you think Tom is important to the plot, then what is his role?