There is a brief yet marvelous conversation in The Lord of the Rings, when Legolas and Gimli walk together through Minas Tirith and talk of the race of Men.
'We will come', said Imrahil; and they parted with courteous words. 'That is a fair lord and a great captain of men,' said Legolas. 'If Gondor has such men still in these days of fading, great must have been its glory in the days of its rising'. 'And doubtless the good stone-work is the older and was wrought in the first building,' said Gimli. 'It is ever so with the things that Men begin: there is a frost in Spring, or a blight in Summer, and they fail of their promise.' 'Yet seldom do they fail of their seed,' said Legolas. 'And that will lie in the dust and rot to spring up again in times and places unlooked-for. The deeds of Men will outlast us, Gimli.' 'And yet come to naught in the end but might-have-beens, I guess,' said the Dwarf. 'To that the Elves know not the answer,' said Legolas.
I have long regarded this as one of the most significant passages in the LotR; yet now I realize that while the exchange gives a correct understanding of Men as it seems from the perspectives of Elf and Dwarf - the Elf-Dwarf perspective is restricted to Men in this world.
Elves and Dwarfs have an existence in both life and after death that is - so far as they know - wholly of this world, this 'planet'. Their lives are therefore bound-up with the life of 'the earth'.
Tolkien links this to the great arts and crafts of these races. Elves and Dwarves can achieve higher standards of work than Men because they both care more about this world, are wholly invested-in this world; and the permanent link to this world means that their interest and commitment to their work does not fade.
Men are relatively much more fickle, easily distracted, more readily bored than either Elf or Dwarf; and therefore Men's work, even when it starts-out very well, is less invested-in and tends to decline. And ultimately this is because Men's souls leave this-world after death.
Knowing this innately, Men feel - and behave - like 'visitors' to the world. Visitors are not so much 'at home' as permanent residents.
For Tolkien's Men, and for us - this world does not feel like home, and is not enough.
Consequently, Men are less engaged with the world, and with their work - they do not take this-world as seriously as Elves and Dwarves - and for Men there is a tendency to become dissatisfied, to daydream and lose focus on the work at hand; and to aspire after something beyond the world...
To understand the perspective of Men, therefore, we must take into account Aragorn's words on his deathbed: "Behold! we are not bound for ever to the circles of the world, and beyond them is more than memory."
For Men, but not for Tolkien's Elves and Dwarves, this mortal life is a phase and a preparation; and can be a temporary prelude to something greater and eternal.
Therefore Legolas and Gimli's understanding is incomplete, and they cannot comprehend the fate of Men as including something that lies beyond this-world.
Gimli seems to regard Men as 'merely' shorter lived, less serious and less skilful Dwarves! Legolas balances this with approval of Men's capacity to bounce-back after disaster defeat and to start over again - in a way that Elves - burdened by their long lives and accumulated memories - cannot.
Tolkien did not wish to make the fate of Men any plainer than the 'negative' statement that their souls left this world after death. At the time of LotR, the salvation brought by Jesus Christ was imagined to be a long way in the future; not known by revelation, yet perhaps vaguely intuited...
But Men such as Aragorn who trusted The One (Eru Illuvatar - the prime creator) already knew that there 'must be' some very good reason why Men died and their souls left this world; which was why mortality was called The One's Gift to Men.
Even the Valar could not take this form of death from Men; albeit afte the fall of Morgoth, the Valar extended the lives of Numenorean Men several-fold compared with their earlier ancestors.
Yet even this life extension - which was kindly intended, as a reward and to allow for greater (more Elvish, or Dwarf-like!) levels of skill and achievement in this world - backfired and led ultimately to Men of Numenor desiring the unending life-in-this-world of the Elves and Valar; and to their ultimate corruption and downfall.
Tolkien's lesson, overall, seems to be that Men are what they are - not second-rate elves or Dwarves! - and Men have their own distinctive destiny.
And 'what Men are' includes a perspective larger than that of Elves and Dwarves: a perspective that ought-to extend beyond the death of the body, and beyond the circles of this world.