(What follows is post 4 of 11 exploring the mystery of Tom Bombadil)
Tom as One of the Maiar?
The theory that Tom is one of the Maiar is a theory with much strength, yet in the end it possesses such great weaknesses it also must be discarded. This theory operates as the default theory that most Tolkien fans adopt. It will be demonstrated that this theory does not answer the problem of Bombadil well at all. Of the three questions about Tom listed above none are adequately answered by this theory. From what we know of the Maiar and what we know of Tom it becomes rather tenuous to hold him to be one of the Maiar.
The first area is Tom's unique power over the Forest and over demons (Barrow-wights). It is conceivable that a Maiar would possess power over both dynamics (Forest & Demons) so here we find a possible strength for this theory. But once one looks deeper into what we know about the Maiar already in Middle Earth it seems that Tom is too powerful to be one. Gandalf, though never faced with a Barrow-wight or Old Man Willow, faces many battles against similar creatures. In none of these battles does the power of his voice through singing ever affect a creature the way Tom's does. Gandalf and Saruman use spells to combat challenges, Tom uses song. By a mere song Tom gets a demon to no longer exist, Gandalf on the other hand often has to resort to his sword and staff to combat evil forces. This is indeed circumstantial evidence but what we know of the Maiar in Middle Earth should inform our opinion of the possibility of Tom being one. So the first point is neither an area of great strength for this theory nor it is too great of an area of weakness as to not be overcome. So in the spirit of charity we will call this question a draw with both strengths and weaknesses.
The second area is Tom's relationship with the Ring. This area presents perhaps the biggest blow to any suggestion that Tom is one of the Maiar. Tom places the Ring on his finger and is not affected by it. The Ring has no power over him as Gandalf at the Council of Elrond states, “Say rather that the Ring has no power over him” (FOTR, 384). Tom also has no desire for the Ring and he would not see any need to keep it nor protect it. All of what we know about Tom and the Ring flies shockingly in the face of what we know of other Maiar and their relationship to the Ring. Gandalf, Saruman, and Sauron are all under the power of the Ring and all three to varying degrees are tempted by the Ring. Tolkien himself puts it this way, “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 then state and content of that part of the Universe" (Tolkien Letter 153). The power the Ring has over any embodied Maiar must be recognized. If Tom were a Maiar, he would not be free from the influence of the Ring as we are plainly told he is. Let us not forget Gandalf’s plea to Frodo to not tempt him with the Ring! Question two leaves the Maiar theory greatly weakened.
Also, the fact that Tom would see no need to protect the Ring and that he would lose it flies in the face of what we know of other Maiar. Most definitely a Maia would know the significance of the Ring and would not lose it due to absent-mindedness. A Maiar would recognize the threat Sauron, a fellow Maiar, would present if he had the Ring.
The third area yet again presents severe difficulties for the idea that Tom is a Maiar, Tom’s age. The idea of presenting a Maiar as "Fatherless" is not as troublesome yet the other comments of his age and role present insurmountable difficulties to this theory. Tom says of himself:
“Eldest, that’s what I am. Mark my words, my friends: Tom was here before the river and the trees; Tom remembers the first raindrop and the first acorn. He made paths before the Big People, and saw the little People arriving. He was here when…the elves passed westward, Tom was here already, before the seas were bent. He knew dark under the stars when it was fearless—before the Dark Lord came from the Outside” (In the House of Tom Bombadil, LOTR, 182).
Tom states that he was here before Morgoth which means it is clear that he cannot be a Maiar. For we know from the Silmarillion that the Valar were first to Middle Earth. Indeed, the elves in the Council of Elrond say that Tom will be "last" as he was "first" if Sauron should win. This description does not fit well with that of a Maiar. Indeed, Gandalf himself puts the nail in coffin when he says of Tom, "He belongs to a much older generation, and my ways are not his" (The Treason of Isengard, 158). While this passage is not canon it is interesting that Gandalf goes out his way to draw a distinction between himself and Tom. Gandalf goes out his way to draw a distinction between himself and Tom. Gandalf clearly tells us that his generation and Tom's are different. Tom’s is much older. Also, their ways are different. Gandalf has drawn a stark distinction between Tom and himself. If Tom were a fellow Maiar there would be no need for Gandalf to draw such a distinction. Tolkien here, through the mouth of Gandalf, tells us that Gandalf is a different creature than Tom is.
How about a Maiar being first and last as Tom is described? Is this a good description of a Maia? No. The Valar are plainly stated to be the first creations in the thought of Iluvatar and are thus the first of the Ainur (Valar & Maiar). Would a Maiar be eldest? No. The Valar are. The theory can only partially answer this questions and the lack of depth and the difficulties of the facts this theory ignores leaves its answers very unsatisfying.
What Glorfindel says about Tom at the Council of Elrond should also give us pause. Glorfindel is one of the High Elves who has been in Valinor and spent time with both the Maiar and the Valar. Yet he has no idea what Tom is. Surely if Tom was a Maiar or a Valar for that matter, Glorfindel would not be so perplexed. This, coinciding with Gandalf’s distancing of himself from Tom, should give us great pause in considering Tom to be a Maiar. From what we know of the Maiar in Middle Earth in this time, what we know of Tom, it becomes clear that this theory amounts to trying to fit a square peg into a round hole. If we change what we know of the Maiar, and make all kinds of adaptations to make what we know of the Maiar to make them more like Tom, then sure Tom could be one of the Maiar, but that is not how Tolkien has revealed the Maiar nor Tom to us in the text. With a lot of effort one can try to forcefully get that square peg into the round hole but there are better options available which can better explain what we know of Tom.
Further Objections: A More Powerful Maia?
Some proponents of the Maiar theory would reply to my objections, "Perhaps the Ring has no power over Tom because he is a more powerful Maia than Sauron or Gandalf is." While I agree that in some sense Tom is too powerful to be a Maia, yet this rebuttal makes the possibility of Tom being a Maia even more difficult. Why? Let me explain. If Tom is a Maia who is more powerful than Sauron, thus free of his craft (the Ring) ,we have no fewer than two more problems. First, this suggestion operates under the assumption that power is what can overcome the Ring, which is contrary to what the whole story of Lord of the Rings teaches us. It is the weak who are needed not the powerful. The more power one has the more tempted they seem to be to take the Ring and try to use it. Gandalf turns down the Ring because he is powerful and through him the Ring would wield a power too great to be imagined.
A few examples from the Lord of the Rings and Tolkien's Letters will demonstrate the reality that being more powerful is not how one controls the Ring, nor is it how one is immune to its influence. Rather, the more power one has the more suspectible they are to the Ring. First a look at the big picture, the moral of the entire story, Tolkien writes:
You can make the Ring into an allegory of our own time, if you like: an allegory of the inevitable fate that waits all attempts to defeat evil power by power. (Tolkien's Letters, #109, 121).
Tolkien makes it plain that the metaphor of the Ring is the reality that power is suspectible to being corrupted. This is demonstrated further by a theoritical situation Tolkien throws out about someone of more natural power than Frodo possessing the Ring:
A person of greater native power [than Frodo] could probably never have resisted the Ring’s lure so long. (Tolkien's Letters, #181, 233-234)
If someone has more power than Frodo, who admittedly is the little-guy with realitvely no power in comparison to Maiar, Valar, and Elves, they would be more suspectible to the corrupting nature of the Ring not less. This includes the angelic realm. Sauron, the Balrogs, and Saruman all fell and lost their unfallen standing, so we know it is possible for these creatures to be corrupted. And Gandalf knows that he would fall to the Ring, which is why when he is offered the Ring by Frodo he says:
‘No!’ cried Gandalf… ‘With that power I should have power too great and terrible. Over me the Ring would gain a power still greater and more deadly…Do not tempt me! I do not wish to become like the Dark Lord himself. Yet the way of the Ring to my heart is by pity, pity for weakness and the desire of strength to do good…The wish to wield it would be too great for my strength. (FoTR, The Shadow of the Past, 95).
It is clear that Gandalf knows that he would fall to the Ring, not to Sauron. The Ring would corrupt his good desires to do good and he would fall. Notice also that he says, "the Ring would gain a power still greater and more deadly." That's right, the Ring would gain power through its use of Gandalf. The Ring feeds off of the power of its wearer. It corrupts through the inherent power of the bearer. So any suggestion that Tom is a more powerful Maia (or a Vala for that matter because the Valar are simply the rulers of the Ainur, hence they are just really powerful Ainur and Maiar are less powerful Ainur) is pure nonsense. If Tom were a very powerful Maia he would have fell when he took the Ring.
The issue is not that Tom has great power and thus is immune from the Ring, but that he is not in the same order as those who are effected by it (this includes Elves, Men, Dwarves, Ainur, etc). We are told as much in the Council of Elrond:
'Could we not still send messages to him [Bombadil] and obtain his help?' asked Erestor. 'It seems that he has a power even over the Ring.'
'No, I should not put it so,' said Gandalf. 'Say rather that the Ring has no power over him. He is his own Master." (LoTR, The Council of Elrond, 348)
Notice that when Erestor says that Tom has power over the Ring Gandalf corrects him. The issue of Tom's immunity to the Ring is not because of his power but it is because he is his own Master. Tom is utterly different then anything else we encounter. Any suggestion that power is why Tom escapes the influence of the Ring must be abandoned because Tolkien through Gandalf dismisses it for us. Increasing the theoretical power of a Maia only creates more issues it does not solve anything.
The second problem for this suggestion is even more troublesome. If Tom is more powerful than Sauron then why could he not defeat him? This is not merely Tom versus Sauron and his armies, the context of us being told that Tom could not defeat Sauron is if the Council decided to give Tom the One Ruling Ring. That's right: Tom with the Ring could not defeat Sauron who would not have his Ring. Considering that both Gandalf and Saruman operate under the belief that if they took control of the Ring they would surely defeat Sauron this solution fails miserably. So clearly Tom is not a Maia of greater stature than Sauron otherwise he would be able to defeat the ringless Sauron. Indeed, he would have been able to control all of Sauron's armies. This fact not only greatly hurts the Maiar theory it is yet another reason Tom cannot be a Vala also. The solution of merely making Tom more powerful than Sauron is simply impossible. Tom's power must be different in essence not just amount in order to explain why the Ring has no influence over him.
So the proponents of the Maiar theory would be right to suggest in response to this that Tom must be a less powerful Maia than Sauron and now we have the problem of why the Ring has no power over him at all? Neither solution helps this theory out, rather both suggestions magnify the problems of this flawed theory and show why the Maiar theory cannot hold-up when it worked out thoroughly.
We are left with only one response to the suggestion that Tom is one of the Maiar, we must firmly reject it. This theory simply cannot account for the all the data we know about Tom , the Ring, and the Maiar. Sadly, this theory falls short of explaining the mystery that is Tom Bombadil. Now we will explore the possibility of Tom being a Nature Spirit.
Continues with the Nature Spirit Theory
 Admittedly “Fatherless and Eldest” better describes the Valar than the Maiar but for sake of argument we will overlook that for now.
 Because Tom lists himself as being here before the Elves and Men, plus before trees, rivers, rain, acorns, and oceans it is necessary that the Dark Lord in reference here is none other than Morgoth at the beginning of time before darkness entailed evil and fear when the Dark Lord came from the Outside. Sauron came from the outside with Morgoth and then remained in Middle Earth never leaving and returning again. So this reference must be to Morgoth not Sauron.
 Ainulindale, 9-11, recounts darkness entering the world and when Melkor enter Ea while the Valar worked on forming Ea. Also we are told in the Silmarillion (27) that at the beginning of time Yavanna planted seeds and brought life to the Earth, Tom had to be there before that time.