How we cite our quotes: All quotations are from the director's cut of The Fellowship of the Ring.
Quote #1
BOROMIR [to Frodo]: What chance do you think you have? They will find you. They will take the Ring and you will beg for death before the end. You fool! It is not yours save by unhappy chance... it might have been mine. It should be mine. Give it to me! Give me the ring.
At the climax of betrayal, Boromir seems to be making some pretty reasonable arguments. What chance does Frodo have? Not a good one. And why does Frodo get to carry it? Just because it randomly fell into the hands of his uncle? But Boromir, his will superseded by the Ring's will, falls into pure greed and grabs Frodo, trying to take it from him.
Quote #2
BOROMIR [to invisible Frodo]: I see your mind. You will take the Ring to Sauron. You will betray us! You go to your death and the death of us all.
Boromir is probably just saying outlandish things because he's upset at his failure to take the Ring from Frodo.
Quote #3
GANDALF: Tell me, friend,when did Saruman the Wise abandon reason for madness?
[A brief scuffle ensues; Saruman is victorious.]
SARUMAN: I gave you the chance of aiding me willingly. But you have elected the way of pain!
This is betrayal on a truly terrifying level. Saruman is the wisest of wise, the leader of the Istari. He is literally a god incarnate. Gandalf isn't just losing a counselor; Middle-earth is losing a great ally. Saruman's betrayal shows us that even the wisest can be corrupted.