Boromir is a fascinating, if odd, character in LOTR; in a letter,
Tolkien cites him as being ignored by early critics who dismissed his characters as simplistically black or white, good or
evil. This discomfort has continued, as a notable paucity of index entries for him in critical studies will confirm.
He's "odd" because he's a typical High Mimetic tragic hero, incongruously stuck in a Romance story, where we
do expect to see characters fall on one side or the other of the good/evil divide. The tragic hero's arc is like an inverted U: he has a great destiny nearly in his grasp, when at the pinnacle, but the last step is an act which causes his fall, whether through hubris, Aristotle's
hamartia, or some other reason. I'd hesitate to use
Balrog's word "arrogant" here; to invoke an image popular in the Middle
Ages, he is at this point at the top of the Wheel of Fortune, too dizzy to see or reason clearly, until he falls from the height -- a literal height, with a literal fall, in Bormir's case. Only then comes the
anagnorsis, the tragic recognition: "What have I said? What have I done?" "I have failed".
Questions of the nature of evil are relevant to the discussion, as they always are with Tolkien, where a tension between different
concepts is ever-present. Shippey talks about this, calling it the difference between a "Boethian" view of evil as the mere absence of good, and a "Manichaean" view of evil as an active force. It's present in the descriptions of
the Ring, from the very beginning, when
Gandalf asks
Frodo to give it to him "for a moment":
It or
Frodo; is the Ring actively evil, or does the evil ("sin") come from within the person, drawn out by the desire for the power that seems inherent in the Ring? This ambivalence, or ambiguity, occurs at
Bree, and throughout. The first is the view of "
the Wise", Gandalf and the
Elves; the other is, to use another of Shippey's terms, as a sort of "psychic amplifier" -- a powerful tool, which could be used for good or evil purpose, depending on the user. This appears to be approximately Boromir's view, in which he was mistaken, but understandably so, given the ambiguities surrounding it.