Neithan Tol Turambar

Boromir was bound by his duty to Gondor and the Steward to slay Aragorn by any means necessary, and the others of the company should they present a threat. His duty to protect Gondor was the single greatest purpose and mandate in his life. He was born just so that he could perform this duty. He honestly and truly believed that the Ring had the power to save Minas Tirith and that Gandalfs hope would bring ruin on Minas Tirith. Therefore he was bound to get the ring and use it to the last defense, and, possible, the defeat of Sauron. Much of his thought was that the words of the dream came to him as just such a directive. But their were also the words to reference the return of the king. So Boromir was in a quandry of several aspects.
1). his love and duty to lord and city
2). the desire long entertained of his own glory
Between these his duty was clear, take the Ring.
The quandry:
3). How to perform his duty in an honorable and manful way as befits a captain of Gondor, Man of the West.
It was not for fear of Aragorn that he chose not to directly confront him. Nor for knowledge that Gimli and Legolas would hinder him, and that such a direct confrontation would end in failure.
The reason for his deciding not to perform his duty in that fashion was because the responsibility of his own discretion in the matter was become beholden to that of the will of Aragorn. For the love that Boromir found in his heart for the Ranger of the North. He found to his suprise and delight and pain that he loved and respected Aragorn, and heeded willfully to his counsel, not just because, though at first he doubted, he had come to accept the veracity of Aragorns claim on the Sceptor, but even more so because in any other circumstances, would by some chance of Fate he were not the Son of the Steward of Gondor, still he would have followed Aragorn, and took him willingly and lovingly as his lord. Such was the dignity of the character of Aragorn, even apart from his lineage.
Boromir would still have been right in his attempt to wrest the ring from Frodo, unscrupulous though the need made of it, the reason he knew that he had done evil was because he percieved in the very midst of his folly that by doing so, he had allowed himself to be decieved, and that his duty before the Steward of Gondor was to follow the counsel of Aragorn. In his desire to take the ring he percieved that it was not for his duty to Gondor, but for the evil desire of the Ring.
He collapsed with grief. Aragorn gave him his final command.
In the moment of his death he does not see Strider, or even Aragorn, but the revealed Majesty of the King of the West. Yeah, maybe even a vision in part of Elendil himself. And what he took as a damnning failure, the greatest ignoble defeat he could have ever suffered in life, never even dreamed of, yet horribly real and true, was in that moment turned to his greatest victory. People say here have said 'fogiveness' and 'pardon'. Don't you see it was so much greater than that? His victory as revealed by the King was won; his, justly and deserved. And then he smiled. The departure of Boromir I believe is the greatest scene in all of literture, reigning supreme without a rival.
Thanks.