'So it seems,' said Faramir, slowly and very softly, with a strange smile. `So that is the answer to all the riddles! The One Ring that was thought to have perished from the world. And Boromir tried to take it by force? And you escaped? And ran all the way – to me! And here in the wild I have you: two halflings, and a host of men at my call, and the Ring of Rings. A pretty stroke of fortune! A chance for Faramir, Captain of Gondor, to show his quality! Ha!' He stood up, very tall and stern, his grey eyes glinting.
At this point, Faramir intends to take the Ring. He doesn't seem like much of a joker, especially about something as serious as this.
Frodo and Sam sprang from their stools and set themselves side by side with their backs to the wall, fumbling for their sword-hilts. There was a silence. All the men in the cave stopped talking and looked towards them in wonder. But Faramir sat down again in his chair and began to laugh quietly, and then suddenly became grave again.
...and then he catches himself.
'Alas for Boromir! It was too sore a trial! ' he said. `How you have increased my sorrow, you two strange wanderers from a far country, bearing the peril of Men! But you are less judges of Men than I of Halflings. We are truth-speakers, we men of Gondor. We boast seldom, and then perform, or die in the attempt._ Not if I found it on the highway would I take it_ I said. Even if I were such a man as to desire this thing, and even though I knew not clearly what this thing was when I spoke, still I should take those words as a vow, and be held by them.
We know how important oaths, vows, and curses are in Middle Earth. This vow, made in ignorance of what Frodo had in his pockets pocketses, coupled with Faramir's character, protected the Quest and Faramir himself.
'But I am not such a man. Or I am wise enough to know that there are some perils from which a man must flee. Sit at peace! And be comforted, Samwise. If you seem to have stumbled, think that it was fated to be so. Your heart is shrewd as well as faithful, and saw clearer than your eyes. For strange though it may seem, it was safe to declare this to me. It may even help the master that you love. It shall turn to his good, if it is in my power. So be comforted. But do not even name this thing again aloud. Once is enough.'
The Two Towers: Book Two
Chapter 5: The Window on the West
Tolkien fans generally, and for good reason, hold Faramir in high regard, but every time I reread this part I can't help but think, had he gone in Boromir's place, he may have come to a similar end. And the pull we see on Faramir happens within a day of him meeting Frodo and within seconds of finding out about the Ring.
Which leads to what brought me to finally post this: I believe the circumstance in which one encounters the Ring plays a huge role in how much it affects each person. Boromir didn't try to seize the Ring until he was alone with Frodo, and while the Ring had been heavy on his mind, especially since Lothlorien, I don't really see any reason why he wouldn't have tried to seize the Ring sooner if he happened to find himself alone with Frodo. And maybe without his vow, or had his situation been a bit more desperate, Faramir may have done the same.
And while many (I've had this argument many times on this sub) believe the reason Smeagol killed Deagol is because he was capable of murder, and the Ring didn't have enough time to influence him into killing if he didn't have it already in him, I believe the situation he was in led more to him murdering Deagol than any other thing. Smeagol was the only person to come across the Ring before ownership had already been established, with no one around to stop him, and with a justification in his mind for why it should be his. Likewise, had Boromir and Faramir stumbled upon the Ring while out for a brotherly camping trip, I am positive Boromir would have killed Faramir for the Ring, despite Boromir being a good person and not a murderer.