The Gift of Men refers to a gift of Ilúvatar to his Younger Children, which remains a source of some confusion for Tolkien enthusiasts. The concept includes both mortality and free will. Below are two interpretations of the nature and extent of the Gift of Men as articulated by Tolkien.
A spiritual/theological view of the Gift of Men Edit
The Gift of Men was an act of the Supreme Being Ilúvatar that set the race of Men apart from the Elves. While the race of Elves would know the most bliss and contentment and would conceive more beauty than any others of the Children of Ilúvatar, it was decreed by this gift that Men would be the prime instruments of Ilúvatar within Arda.
Ilúvatar willed that the spirits/hearts of Men are not content within Arda, and find no rest therein, and therefore seek beyond the world and its confines. They are not bound to the Circles of the World, as the Elves and all other creatures of Arda are bound to the Earth. The spirits of Men truly leave the physical world, and do not return. Thus their fates are completely sundered from that of the Elves, who do not die until the world dies, unless slain by violence or ill chance, or by wearying at the last of the passage of centuries. But as the years grow long and Time wears, even the Valar will come to envy the gift of Ilúvatar to the race of Men, that of liberation from the physical world, and the inevitability of loss and sorrows that must come with this existence within Arda.
Moreover, it is also a consequence of this true spiritual freedom of not being bound to either the ordinance of Fate, or the confines of the World that the spirits of Men do not dwell long in Arda, and after what seems to be a very short time to the immortal Elves, men age, grow weary, and die.
However, a key aspect of this gift of living within Arda for a short time was a virtue instilled into the race of Men to be motivated to create destinies for themselves amidst the powers and chances of the world. Men were able to shape their lives beyond the Music of the Ainur, which rules the fates of all other things in Arda. Men may choose to live in tune with the themes of the Music that created Arda, or be indifferent to it, or live in defiance of it.
Ilúvatar understood that Men would not always use this gift of freedom in harmony with the world, and would stray often. But he knew that in their time, men would continue to order their lives within Arda and by their "operation everything should be, in form and deed, completed, and the world fulfilled unto the last and the smallest" (The Silmarillion). Thus Men would become the implements by which Ilúvatar's plans for Arda will be realized in the ages to come.
The Gift, as originally bequeathed, was not something that Men feared. Though they loved their lives within Arda, they relinquished their spirits gracefully, almost gladly, and seemed to pass into a peaceful sleep, never to wake again in this life. But their souls go to a place unknown to the wisest of Elves or even the Valar.
However it is written that when the Second Music of the Ainur is played, after the Dagor Dagorath, the spirits of Men shall be included in this even greater theme, when all of the players will know and understand their part and its relation to the whole, and be tributary to its beauty and glory.
Avoidance of the Gift of Men Edit
The shadow of the first Dark Lord brought with it a perversion of the original intent of the Gift of Ilúvatar, and brought fear out of hope, and tainted the Gift. Men began to fear and despise the gift, and began to view it not as liberation, but as damnation. It brought about in the race of Men a kind of self-loathing and a denial of the basic nature of their being as the children of the All-Father Eru Ilúvatar. Instead they viewed themselves as flawed in some way and sought to resist this very intrinsic nature of their creation. The result of such actions brought about much anguish on the race of Men through the centuries of the history of Arda.
At least four characters in The Lord of the Rings are examples of the dangers of either deliberately or unintentionally trying to avoid the Gift of Men. Three of them are transformed into "monsters" by being denied the Gift of Men by sins that they have committed: the Lord of the Nazgûl (and all of the Nazgûl), the King of the Dead, and Sméagol. (Since Sméagol is a Hobbit-like creature, he is numbered among the Younger Children of Ilúvatar, and as such is entitled to the strange Gift of Men.) The Nazgûl are made immortal, but also doomed, by the Nine Rings. The King of the Dead is transformed into a ghost or monster by the curse of Isildur, because he and his subjects break an oath to fight against Sauron. Long after his natural death, he fulfils his oath, and is released from his condition by Aragorn. (This presumably also applies to the other Dead.) Sméagol is consumed by the Ring; over the years, its influence transforms him from a Hobbit into the freakish Gollum.
Bilbo Baggins, like Sméagol, is a Hobbit rather than a Man, but Hobbits are also among the Younger Children of Ilúvatar, and are therefore recipients of the Gift of Men. Bilbo encounters Gollum in his cave and escapes with the Ring. Being a Hobbit of much better character than Sméagol, Bilbo better resists the negative effects of possessing the One Ring. He does not age, but has a sense of becoming "thin and stretched." Toward the end of his possession of the Ring, Bilbo begins to show some of the obsessive tendencies of Gollum — calling the Ring "my precious," and showing flashes of dark hostility when asked by Gandalf to give the Ring to his heir, Frodo.
Those Men with the greatest understanding treated death as the Gift it was originally intended to be, and when their time came gladly gave themselves up to it. We see this, for example, in the earlier Kings of Númenor, and Aragorn also accepted the Gift at the natural end of his life. For most Men, though, the Gift was tainted by Morgoth, and they came to fear it rather than embrace it. This fear reached its peak in the later years of Númenor, where even the long life given to the Númenóreans was not enough, and wise men did all they could to try to escape death altogether. In the end, this desperation led to Númenor's destruction when Ar-Pharazôn led a battle fleet to the Undying Lands, having been convinced by Sauron's lies that they held the key to the immortality of the Elves.