Gene is the narrator and protagonist of A Separate Peace. He suffers from many of the ailments you're probably all familiar with, or will be shortly, from your own sixteen-year-old days: self-consciousness, uncertainty, jealousy, an identity crisis or two, and really annoying seniors with duck-and-shrubbery related names (Quackenbush, for those of you who don't speak crossword puzzle). What we're saying is, Gene is a generally typical adolescent male – until he goes all Lord of the Flies whacky on his best friend.
Wait a minute. We don't actually know whether or not Gene is responsible for Finny's accident. On the one hand, he was clearly feeling jealous beforehand, he felt better immediately after, he feels guilty as hell a little bit after that, he admits to jouncing the branch, and he even confesses his crime to Phineas. But we can't be sure if that "crime" was accidental, or subconscious, or a blind impulse, or consciously malevolent. When you consider that the source of our facts is Gene himself, the waters get even muddier. It could very well be that Gene, stricken with guilt over accidentally shaking the branch, has imagined these antagonist emotions which, in fact, were never there. Sure, that's a stretch, but the point is that there's a variety of interpretations here, none of them objectively and definitely correct.
Now let's take a look at these emotions which may or may not have led Gene to cause the accident. Just what is Gene's attitude toward Phineas? It's clear from the start that Gene holds a great deal of admiration for his friend. The language used to describe Finny is majestic and epic. He is a hero, an athlete, and a god in Gene's eyes. Naturally, he's also the competition – in sports, yes, but also in conversation, in actions, in the very process of being a student at Devon. Gene may earn better grades, but it is Finny who captivates everyone's attention, who wins them all over, who can corral the boys into any activity and talk even Gene into breaking the rules. Gene resents this. Remember when he's up in the tree and angrily worries that Finny is getting "some sort of hold" over him? Right, well that would be the resentment. There's also a healthy dose of fear – fear that Gene himself is inadequate when faced with such a superior human being.
And that's what makes this all so interesting to watch. Gene both admires and resents, loves and fears his best friend, and that's one hefty grab-bag of emotions. What's interesting, though, is what really pushes Gene over the edge from passive rivalry to active animosity: Finny's goodness. At the end of the day, Gene doesn't resent Finny's athleticism, people-skills, charm, humor, or grace as much as he resents his character. And THAT'S the source of the limb-jouncing business, however you choose to interpret motive.
But enough about Finny's fall – let's look at what happens after it. You may or may not have noticed a series of rather kooky events: Gene puts on Phineas's clothes and stands in front of the mirror; Gene decides to become a part of Phineas; Gene admits that he no longer needs the fake Southern persona he put on when he first came to Devon; he wanders around in the dark and feels like he never existed; and finally, he can't cry at Finny's funeral because he feels as though it is his own. Do you see a common thread here? Yes, that's right – identity. Gene starts to become Phineas.
Oddly enough, this sort of makes sense. One way to think about it is the guilt – Gene is so disgusted with himself for having caused Finny's accident that he can't bear to be Gene anymore. So he becomes someone else: Phineas. Another explanation is that Gene is acting on his admiration and jealousy by trying to become his hero. Another is that Gene is a sixteen-year-old boy struggling to define himself in a difficult time. Rather than craft his own identity, he's simply borrowed someone else's.
This leads us to another interesting aspect of Gene's character: the old Gene. The one telling the story. What's his deal? Has he established his own identity, or is he still harping on Phineas's? Has he made his peace with what happened during the summer of 1942? Has he established, as he ventures in the first chapter, "a growth and harmony" within himself? We'll let you take it from here.