The halls of mandos and elvish "free will"

[HerenIstarion]

He (Eru) willed that the hearts of Men should seek beyond the world and find no rest therein; but they should have a virtue to shape their life amid the powers and chances of the world, beyond the Music of the Ainur, which is a fate to all things else"

Once, in similar discussion (Evil Things) here I answered the quote with the following analogy:

...the world is like train moving on rails, with elves having tickets on to the terminal station while Men keep jumping out of windows now and again. (Or, in more civilized mental picture, having tickets on to intermediary stations). Music is rails.

Or, to elaborate a point just a tiny bit - the free will is expressed by ability of choice, but the choice of elves is contained inside the 'train', whilst men leave it after short journey.

'All things else' of the quote determines the fate of the things of Arda, and includes animals and plants, as they do not have fëar, theirs being the mode of existence made up of matter entirely, and as matter is finite, so are they. Elves are included in 'all things else' as their fëar are bound with the world and doomed to remain there (though there is a hope for elves after the 'end of the world' too, see continuation of the discussion in the same thread)

I know, I think in analogies

Black ants, red ants...