The Fandom LOTR wiki lists four times Eru Ilúvatar intervened in the history of Arda:
In a letter written by Tolkien, he stated that Eru again intervened, this time in the Third Age, causing Gollum to trip and fall into the fires of Mount Doom while still holding the One Ring, thus destroying it.
Is this correct? If so, what letter is this, and exactly what did Tolkien say?
Yes, as we can see on Letter #192, Eru certainly took over after Frodo was done with the assigned task.
Tolkien mentions that Frodo did take the Ring to a certain point (where no other being could) and then another power took over to decide the fate of the Ring.
Frodo deserved all honour because he spent every drop of his power of will and body, and that was just sufficient to bring him to the destined point, and no further. Few others, possibly no others of his time, would have got so far. The Other Power then took over: the Writer of the Story (by which I do not mean myself), 'that one ever-present Person who is never absent and never named' (as one critic has said).
See Vol. I p. 65. 2 A third (the only other) commentator on the point some months ago reviled Frodo as a scoundrel (who should have been hung and not honoured), and me too. It seems sad and strange that, in this evil time when daily people of good will are tortured, 'brainwashed', and broken, anyone could be so fiercely simpleminded and self righteous.
(Emphasis mine)
Exact quote is from the second link here, page 270; cannot post the direct link
Earlier in the book, when Gollum is made to swear fealty to Frodo before the ring, Frodo warns Gollum that oaths by the ring aren't to be taken lightly.
Later on, when Sam and Frodo had almost reached the end, Gollum attacks them - to which Frodo says "If you touch me ever again, you shall be cast yourself into the Fire of Doom." It seems to me that, since the ring at this point has absolute power over Gollum, and Frodo is the ring bearer, this is treated as another oath before the ring. It is therefore Gollum's own enslavement to the ring that forces him to fulfill that oath and fall into the fire after he attacks Frodo.
Nicely done @Shevliaskovic, I thought I was the only person who caught that.
But there is also the fact that Gollum never actually swore to serve Frodo, he swore to serve the Master of the Precious:
‘Down! down!’ said Frodo. ‘Now speak your promise!’
‘We promises, yes I promise!’ said Gollum. ‘I will serve the master of the Precious. Good master, good Sméagol, gollum, gollum!’ Suddenly he began to weep and bite at his ankle again.
And we know from the Silmarillion that:
Then Ilúvatar spoke, and he said: 'Mighty are the Ainur, and mightiest among them is Melkor; but that he may know, and all the Ainur, that I am Ilúvatar, those things that ye have sung, I will show them forth, that ye may see what ye have done. And thou, Melkor, shalt see that no theme may be played that hath not its uttermost source in me, nor can any alter the music in my despite. For he that attempteth this shall prove but mine instrument in the devising of things more wonderful, which he himself hath not imagined.'
So wouldn't it be a twist of irony if, as this passage indicates, the "Master of the Precious" is not Frodo, nor Sauron even, but Ilúvatar himself? And that absolves Gollum, somewhat, because in the end he did serve Ilúvatar's purpose, a purpose which Gandalf foresaw.
I agree, in a way. Eru did not actually trip Gollum, but He made certain all the right conditions were there for the grand finale:
He made certain that Sauron did not kill his captive, as he should have done.
Gollum was captured in Mordor in the year 3017 and taken to Barad-dûr, and there questioned and tormented. When he had learned what he could from him, Sauron released him and sent him forth again. He did not trust Gollum, for he divined something indomitable in him, which could not be overcome, even by the Shadow of Fear, except by destroying him. [...] Ultimately indomitable he was, except by death, as Sauron did not fully comprehend, being himself consumed by lust for the Ring.
–J.R.R. Tolkien, Unfinished Tales, "The Hunt for the Ring”
What was that which made such a weak-willed person so strong against the greatest evil on the face of Arda? The destiny which Eru had in place for him. Sauron told himself that he would use Gollum as a bloodhound, however the creature was notoriously sneaky and elusive and he already had the Nazgul, for which the One worked as a beacon in the night. Gollum was a liability for Sauron, not any kind of help.
Gollum, when he finally managed to grasp his Precious again, had been separated from it for almost 60 years, a lifetime in human terms. I know some find the parallel between a junkie and Gollum disturbing or foreign to the context of high fantasy, but it is quite accurate: Gollum is hopelessly addicted to the One to the point of obsession, while at the same time it is the thing which utterly and completely ruined his life, twisting his body and soul. And much like a drug addict suffering from extreme withdrawal, once he gets his hands on the object of his desire he ODs. In this case he lost all sense of where he was, and in his absolute bliss he merrily dances himself (and the One) to his demise.
Tolkien had explained to those who thought that Frodo was a failure that there was no one alive on Middle-earth at the time who would have managed to get even that far. It was simply impossible for anyone to willingly destroy the Ring. Therefore, Gollum had this critical role to play at the end. Ironically, the very power of the Ring, to possess the mind of its bearer and strip them of rational thought, making itself the most precious thing in the world for the bearer, was ultimately the very cause of its destruction. That, and of course the mercy shown to Gollum by both Bilbo and Frodo.
One very interesting side question is who was it that spoke to Gollum in Sam's vision of Frodo as a white-robed figure with a wheel of fire, on the slopes of Mount Doom? Given the above and Tolkien's own quote about Eru taking over, I would say that it was Eru himself, speaking as Frodo and giving fair warning to Gollum about his impending doom. If we accept all the above to be true, then Eru would have been manipulating poor Smeagol for most of his wretched life. That would not sit at all well with a devout Catholic, such as Tolkien. Therefore He would have to offer Gollum a warning and a chance at redemption, even if Eru knew precisely what would happen in the end.
I recently read a Greek play- Iphigenia among the Tauriens, and at the end the protagonists are trying to escape on a ship, but the winds turn against them, and are going to force them back to shore to be killed. Athena then intervenes and turns the winds back to blow them to Greece. The play is a tragedy, but some people say that it isn't because of the happy ending. In my class I'm taking where we discussed this, we learned that this makes the play MORE tragic, because it shows that even if you do everything right, you still might fail because you are at the mercy of higher powers. I think this is what Tolkien is doing, and has Iluvatar trip Gollum to show that we are all at the mercy of God, nature, dumb luck, etc.
I think, in Gollum taking the Ring and falling, Tolkien is saying a few things...that unprincipled lust without restraint will lead to one's ultimate downfall (the tale is not so different from the oath of the Silmarils), that (in Frodo's circumstance), great courage in the face of hardship (he was "meant" to have the ring) allows fate to intervene better than cowardice would, and also, that there is a higher power, because, as I recall (let's forget the movie and think about the book, and I don't have chapter and verse in front of me to cite), when Gollum swears his oath to Frodo, he swears "on the precious". When Frodo overhears Gollum plotting, he reminds him of his oath, and says something along the lines of "if you break your oath, I will see you cast into the very death that is the destiny of the ring" (excuse my paraphrasing, I have guests sleeping in my library). I think this is a bigger scene in the book than most people realize - and that Tolkien is setting up the ultimate irony. Gollum's lust for the ring is similar to a junkie sticking a needle in his arm - it's irresistible, empowering, but he knows it will ultimately kill him... he has lost the ability of free will. I do not make a religious statement, so much as explore the amazingly complex literary devise that even Shakespeare would envy.
