[Huinesoron]

Originally Posted by TY 2300

These children [Elladan, Elrohir, Arwen] were three parts of Elven-race, but the doom spoken at their birth was that they should live even as the Elves so long as their father remained in Middle-earth; but if he departed they should have then the choice either to pass over the Sea with him, or to become mortal, if they remained behind.

Originally Posted by Morthoron

Tolkien, Professor of Anglo-Saxon as he was, is using the word "doom" in the Old English sense, "judgement". Mandos makes an irrevocable pronouncement on the fates of those entwined. He does offer a choice to Elros and Elrond, and the children of Elrond, but again, once that choice is made it cannot be revoked unto the end of Arda.

Normally I would agree with you, but neither Mandos nor Manwe made any pronouncements at the birth of the El-twins and Arwen, down in the Third Age. (I mean, they may have done, but it would have been in Valinor - Elrond wouldn't have known about it!) This "doom" is also more specific than just "they shall have a choice" - it sets specific time limits on when those three would have to make it.

The Appendices actually use "doom" twice, back to back, to refer to the fates of Aragorn and Arwen:

Originally Posted by Tale of Aragorn and Arwen

But Elrond saw many things and read many hearts. One day, therefore, before the fall of the year he called Aragorn to his chamber, and he said: "Aragorn, Arathorn's son, Lord of the Dúnedain, listen to me! A great doom awaits you, either to rise above the height of all your fathers since the days of Elendil, or to fall into darkness with all that is left of your kin. Many years of trial lie before you. You shall neither have wife, nor bind any woman to you in troth, until your time comes and you are found worthy of it."

Then Aragorn was troubled, and he said: "Can it be that my mother has spoken of this?"

"No indeed," said Elrond. "Your own eyes have betrayed you. But I do not speak of my daughter alone. You shall be betrothed to no man's child as yet. But as for Arwen the Fair, Lady of Imladris and of Lórien, Evenstar of her people, she is of lineage greater than yours, and she has lived in the world already so long that to her you are but as a yearling shoot beside a young birch of many summers. She is too far above you. And so, I think, it may well seem to her. But even if it were not so, and her heart turned towards you, I should still be grieved because of the doom that is laid on us."

"What is that doom?" said Aragorn.

"That so long as I abide here, she shall live with the youth of the Eldar," answered Elrond, "and when I depart, she shall go with them, if she so chooses."

Aragorn's Doom is based on Elrond's observation and reading of hearts; and presumably on the prophecies of Malbeth the Seer, Ivorwen mother of Gilraen, and probably Gilraen herself. If Arwen had a Doom laid on her at birth, as the Tale of Years says, and if that Doom was that she had to choose her fate at the departure of Elrond, then it seems likely that that was of the same kind - a mix of previous and current prophecies and foresights, including the Judgement, but also bringing in other information. Maybe Glorfindel saw something, like he did with the Witch-king; maybe it was Celebrian employing the maternal foresight Tolkien used so often; or maybe it was someone who made no other impact on history.

(Presumably the Doom was originally spoken at the birth of the twins, and then Elrond said "she shall be under the same Doom as her brothers" at Arwen's birth.)

hS