If Denethor hadn't committed suicide

[The Mouth of Sauron]

If Denethor had lived after the Battle of the Pelennor Fields and been introduced to Aragorn, he would have remembered him as Thorongil. And he might legitimately have asked Aragorn why, if his claim to the Kingship was genuine, he didn't press that claim when he served Denethor's father under the guise of Thorongil.

[Inziladun]

Originally Posted by The Mouth of Sauron

If Denethor had lived after the Battle of the Pelennor Fields and been introduced to Aragorn, he would have remembered him as Thorongil. And he might legitimately have asked Aragorn why, if his claim to the Kingship was genuine, he didn't press that claim when he served Denethor's father under the guise of Thorongil.

Interesting. I think the knowledge that 'Thorongil' was truthfully Aragorn probably did belong to Denethor, and that would have played a part in his contesting Aragorn's claim, since Denethor had been jealous of Thorongil's fame and influence with Denethor's father, Ecthelion II.
What would Aragorn's response to Denethor pressing him on that have been? Perhaps something like 'The time was not yet right, Lord Steward. I myself was not ready for the burden, nor had I yet earned it'. I suspect though, that no fair words or deeds on Aragorn's part would have reconciled Denethor to the idea of relinquishing his power and watching Aragorn rule.

[alatar]

Why so negative on Denethor? He was a man at the end of his rope. His eldest son, whom maybe he had invested much hope, had failed and had fallen. His realm, whether he was King or Steward, was about to be swept away. He was estranged from his other son, the son that may have reminded him of the days spent with Finduilas, the son that he's sent to a needless (seemingly) death. Atop this, should some miracle occur and Gondor withstand the coming storm, a challenge to Denethor's leadership had appeared, and Denethor wasn't one to not get his way.

So he despairs at the end. What if, instead of suicide, someone, like Gandalf, knocks the Steward off of the pyre with a spear (hmm...now where have I seen that?) and he lives, though is mortally injured.

Assume the rest of the events play out as they do in RotK. Aragorn then could meet with Denethor, who, now that his realm as been saved, his son alive and installed as Steward, could die in peace after making some conciliatory remarks to Aragorn, showing that, at the end, he upholds the office of the Steward, giving up command as the King has returned. He asks for forgiveness, it's granted, and Denethor dies at peace, after murmuring some line about joining Finduilas and Boromir and Aragorn says something about the nobility of it all (or something).

Too much like Theoden's end?

Then how about Denethor, like his first son, decides to take Gandalf's advice and lead his people in the defense of Minas Tirith. He can then mutter a few lines and die after some duel with something interesting.

[Sarumian]

I totally agree with Alatar that Denethor's end could have happened on the walls of Minas Tirith or during a desperate attempt to stop Witch King from entering the city if he had followed Gandalf's advice.

It's all looks more complex if he had survived. It looks to me as if Denethor has fallen under the spell of the ring just by knowing about it as Sauman did. But with the end of Sauron and the ring Denethor could have recovered from the spell. In this case he might have changed his view of Aragorn, especially after Aragorn saves Faramir. So Denethor could have resigned and either spend his time with Faramir's family or travel along Boromir's pass to Rivendell, where he could have stayed for good learning the lore and compiling memories just like Bilbo.

[Kitanna]

Originally Posted by Sarumian

It's all looks more complex if he had survived. It looks to me as if Denethor has fallen under the spell of the ring just by knowing about it as Sauman did. But with the end of Sauron and the ring Denethor could have recovered from the spell. In this case he might have changed his view of Aragorn, especially after Aragorn saves Faramir.

This is something I hadn't even considered. Look at Theoden. He was under Saruman's spell and distrusted Gandalf, but by the end of his life the spell had been lifted and he was prepared to do what he felt he had too. He also lost a son, his only son, yet when the poison in his life was removed he recovered. It's possible Denethor could have recovered as Theoden had. After all he despaired in part because that was what Sauron wanted.

If Denethor had survived, without Sauron to show ruin in the palantir anymore could it have been possible for him to recover and embrace Aragorn as his king?

[Formendacil]

Originally Posted by Kitanna

If Denethor had survived, without Sauron to show ruin in the palantir anymore could it have been possible for him to recover and embrace Aragorn as his king?

To me this seems a highly unlikely scenario. Denethor's antipathy towards Aragorn--"the last of a ragged house, long bereft of lordship and dignity"--goes deeper than just the poisoning of his mind by the Palantír. Indeed, it seems far more the case to me that while Denethor was somewhat solidified in this position by the use of the Palantír, which gave him a sense of doom and of being the only hope of the West--where was that useless Arnorian lordling, anyway, when needed?--his dislike of Aragorn goes deeper. The Appendices certainly suggest that Denethor had no love for Aragorn:

Originally Posted by Appendix A, I, iv

'There was dismay in the City at the departure of Thorongil, and to all men it seemed a great loss, unless it were to Denethor, son of Ecthelion, a man now ripe for the Stewardship, to which after four years he succeeded on the death of his father.

Clearly, Denethor saw his own position endangered by Thorongil then, and was "ripe" for ruling--which I would read to mean not only "ready," but, in this context, "eager." However, the passage has more to say:

Originally Posted by Appendix A, I, iv

Denether II was a proud man, tall, valiant, and more kingly than any man that had appeared in Gondor for many lives of men; and he was wise also, and far-sighted, and learned in lore. Indeed he was as like to Thorongil as to one of nearest kin, and yet was ever placed second to the stranger in the hears of men and the esteem of his father.

Ouch! Denethor, then, had personal reasons to dislike Aragorn--imagine being made second in your own father's affections? Let's finish quoting this passage, for the sake of completion.

Originally Posted by Appendix A, I, iv

At the time many though that Thornginl had departed before his rival became his master; though indeed Thorongil had never vied with Denethor, nor held himself higher than the servant of his father. And in one matter only were their counsels to the Steward at variance: Thorongil often warned Ecthelion not to put trust in Saruman the White in Isengard, but to welcome rather Gandalf the Grey. But the was little love between Denethor and Gandalf; and after the days of Ecthelion there was less welcome for the Grey Pilgrim in Minas Tirith. Therefore later, when all was made clear, many believed that Denethor, who was subtle in mind and looked further and deeper than other men of his day, had discovered who this stranger Thorongil in truth was, and suspected that he and Mithrandir designed to supplant him.

Personally, I take this passage to read that Denethor had figured out Aragorn's identity before he ever used the Palantír. And, really, how would the Palantír have confirmed this? It might have shown that Aragorn was a friend of Elves, a Ranger of the North, and high in their ranks... but the confirmation that he was the Heir of Isildur does not seem to me the sort of thing that the Palantír would have been a great help with.

Consequently, had Denethor survived the Siege of Gondor, I do not think he would ever have welcome Aragorn. Rather, it would only seem to him that Aragorn had, indeed, conspired with Gandalf to supplant him, and that the War of the Ring had been the seized upon pretext. Denethor's position is crystalline-clear: "I am the Steward of the House of Anárion. I will not step down to be the dotard chamberlain of an upstart. Even were his claim proved to me, still he comes but from the line of Isildur."

Admittedly, these words are spoken in the fury of his last minutes, but they represent Denethor's convinced opinions on the issue, both personally and legally. Personally, he will not submit to Aragorn, defeated by his old rival in his old age. Additionally, he has convinced himself that Pelendur's precedent must still reject the Heir of Arvedui.

To me, it does seem likely that Denethor would not have mounted a resistance. In acknowledgement of the healing of Faramir and seeing the support of the people, Denethor may well (if alive) have stepped down... but I do not think (barring a miracle) it is sensible to think he could ever have accepted Aragorn as king. At best, he would have kept his mouth shut for the sake of a united Gondor and let Faramir's opinions guide those of his children, so that there would not be another "kinstrife" between the Heirs of Elessar and the Heirs of Denethor.

[The Mouth of Sauron]

Come to think of it, Denethor was a hypocrite - he felt slighted by being second in his Father's affections behind Thorongil - then he subjected Faramir to the same treatment.

[Erendis]

Originally Posted by Formendacil

Personally, I take this passage to read that Denethor had figured out Aragorn's identity before he ever used the Palantír. And, really, how would the Palantír have confirmed this? It might have shown that Aragorn was a friend of Elves, a Ranger of the North, and high in their ranks... but the confirmation that he was the Heir of Isildur does not seem to me the sort of thing that the Palantír would have been a great help with.

But Formedacil,you have mentionned all the clues to help Denethor come to this conclusion with certainty!Imagine it;apart from his obvious characteristics,his foe bears that strange ring,which might have seemed quite familiar to a person with Denethor's knowledge of history and eemm..interest to kingship.He comes from a former Dunedain realm,befriends the Elves,is Elrond's foster son and of high rank among the Rangers of the North(whose true ethnological identity I believe was no secret to him either) ...Too many coinsidences,don't you think?