I don't know if I'm missing the point here, (hey, it happens
) but here's some 'stuffs' of possible interest anyway:
The published Silmarillion
" ... and Mandos under Ilúvatar alone save Manwë knows wither they go after the time of recollection in those silent halls beside the Outer Sea."
"But the sons of Men die indeed, and leave the world; wherefore they are called the Guests, or the Strangers."
From the authors commentary on Athrabeth Finrod Ah Andreth
7)
"Since Men die, without accident, and whether they will to do so or not, their fëar must have a different relation to Time. The Elves believed, though they had no certain information, that the fëar of Men, if disembodied, left Time (sooner or later), and never returned. (Authors note *4 ...)" JRRT
*note 4
"Sooner or later. Because the Elves believed that the fëar of dead Men also went to Mandos (...). There they waited until they were surrendered to Eru. The truth of this is not asserted ..." JRRT
Letters
"The Doom (or the Gift) of Men is mortality, freedom from the circles of the world ... (my edit) ... mortality is not explained mythically: it is a mystery of God of which no more is known than that 'what God has purposed for Men is hidden'." JRRT
"Neither had they of course any special information concerning what 'death' portended for Men. They believed that it meant 'liberation from the circles of the World', and was in that respect to them enviable." JRRT
Sorry that some of that is plucked from context, edited for brevity and vaguely whatnot, but I type one-fingered
The published Silmarillion
" ... and Mandos under Ilúvatar alone save Manwë knows wither they go after the time of recollection in those silent halls beside the Outer Sea."
"But the sons of Men die indeed, and leave the world; wherefore they are called the Guests, or the Strangers."
From the authors commentary on Athrabeth Finrod Ah Andreth
7)
"Since Men die, without accident, and whether they will to do so or not, their fëar must have a different relation to Time. The Elves believed, though they had no certain information, that the fëar of Men, if disembodied, left Time (sooner or later), and never returned. (Authors note *4 ...)" JRRT
*note 4
"Sooner or later. Because the Elves believed that the fëar of dead Men also went to Mandos (...). There they waited until they were surrendered to Eru. The truth of this is not asserted ..." JRRT
Letters
"The Doom (or the Gift) of Men is mortality, freedom from the circles of the world ... (my edit) ... mortality is not explained mythically: it is a mystery of God of which no more is known than that 'what God has purposed for Men is hidden'." JRRT
"Neither had they of course any special information concerning what 'death' portended for Men. They believed that it meant 'liberation from the circles of the World', and was in that respect to them enviable." JRRT
Sorry that some of that is plucked from context, edited for brevity and vaguely whatnot, but I type one-fingered

