[Kalimac]

Hmm. What if Denethor had lived...interesting question. As horrifying as "The Pyre of Denethor" is, it's hard to hide that it's incredibly convenient for the plot that he should check out at that particular time.

Denethor has been slowly going under since his favourite son Boromir died, and has been looking into his Palantir far more than is healthy (not that any Palantir-gazing can really be called healthy, except maybe for Aragorn). He certainly is still powerful; witness those first few scenes with Gandalf and Pippin. But even so, his grasp is getting weaker and he won't see it - when they first arrive in Gondor, it's already a ghost town, and men speak much more of Faramir than they do of Denethor, and certainly the impression is that if they had to pick one to follow, it would be Faramir. Why not? Denethor doesn't seem to have gotten out in ages, whereas Faramir is still fighting in the midst of them. So in the end, had everyone lived, they would likely have gone where Faramir went, that is, to Aragorn.

That being said, I can't see Denethor living very long in any scenario. Even had he been prevented from burning himself, or had never thought to do it, he probably wouldn't survive Aragorn's arrival long. He must know in his heart that Aragorn's claim is just; Denethor does have the longsight, after all, and he's certainly no fool. He would be able to read the truth in Aragorn's mind as soon as he saw him.

So Denethor might have built his pyre later, after people had followed Faramir to join up with Aragorn. Or even had he managed to quell the people through the remains of his power, the knowledge that the true king really had returned and that the past was gone would be eating him up. One way or the other, either of "breaking up" - just getting so depressed that his body couldn't maintain itself any more - or through a more active method, he would have died.