The slight but significant changes Peter Jackson makes in bringing the characters of Aragorn and Boromir to the screen bring these two into more dramatic contrast than in the book. Sparks fly, they are like the Englisman and the Irishman, one focussed, diplomatic and considerate, the other shooting his mouth off, insulting everyone and wearing his heart on his sleeve.
The scene where they meet in the moonlit gallery in Rivendell is typical. Aragorn is reading. Boromir takes a quick look at the pictures but art appreciation is not really his thing and he dives on the sword when he sees Narsil. Never mind the history, give me the weapon. Aragorn is finding out that it is hard to read in the dark, but possibly he is only trying to impress Arwen as an intellectual.
But it is at the Council that these two collide. Boromir is passionate in the cause of Gondor and its predicament is tearing him up. He sees everyone as an enemy and the finger stabbing in accusation comes from love but ends up as anger. Aragorn, a thoughtful, watchful man, knows better than to get in the way of someone angry as Boromir is but Legolas unthinkingly puts them in opposition and Aragorn gets the brunt of Boromir's scorn. Unlike Boromir he holds his feelings in check, swallowing his pride. But the slight raising of his chin shows how close Boromir gets to the bone.
Afraid of the power of the Ring Aragorn examines himself constantly. Boromir, like Lear, but slenderly knows himself, and this is his undoing. He is used to giving way to his feelings and does not notice when they begin to lead him astray, under the influence of the Ring.
If he was just pushing people around we would not care for Boromir. But on the march he shows other feelings too, when he befriends Pippin and Merry, and Aragorn comes to see him as a brother officer. On Caradhras, when Boromir hesitates to give back the Ring, Aragorn looks for a moment as if he fears Boromir. But it is not like fearing an enemy, but fearing one of your own who is a loose cannon. Aragorn's scarred hand clasping and unclasping his sword hilt just behind Frodo's shoulder as he waits for Boromir to give back the Ring is one of the most telling shots in the film, and you feel Aragorn does it without even thinking.
In the second book Gandalf says to Aragorn that Merry and Pippin 'saved' Boromir, and so they did. After his feelings - and the Ring - had led him over a cliff and he had attacked Frodo his desire to protect the hobbits cost him his life, but regained him his honour. Boromir fights not only to save Merry and Pippin, but not to die an outcast. Knowing he is doomed, Boromir seems never to be more alive than in this last fight.
One of the things that marks Aragorn as a leader is his ability to accept situations quickly. He accepts that Frodo is hurt and gets on with trying to get him to Rivendell. He accepts Gandalf's fall and gets the Company moving again. But he cannot accept Boromir's death. Boromir is mortally wounded, but Aragorn fumbles at the arrows as if trying to pull one out, denying to himself that Boromir is dying. It is Boromir who has to say to him 'it is over'.
Boromir is not only dying but is in complete despair; he has seen Merry and Pippin taken captive; he has tried to grab the Ring from Frodo; he has failed the Company and he is sure now that 'The world of men will fall'
The strange electricity between these two characters in the film makes Boromir's despair call up actions from Aragorn that he might not have done if he had considered it more; he buries deeply Boromir's shame of having tried to seize the Ring; he follows the orcs that captured Merry and Pippin; he promises Boromir he will go to Minas Tirith and save his city, 'their' people.
Much has been made, and rightly, of Frodo's loss. But Aragorn suffers loss too. When he steps back and lets the tears fall, it is clear that he has lost more than just a headstrong comrade but a brother.
Just musing! sorry to Boromir and Aragorn fans...:-)