How are codependency and identity related to and shown in A Separate Peace?

Gene and Finny's friendship is defined by
codependency, with each relying on the other to bring happiness to his life.
At first, Gene and Finny seem to be normal teenagers. But Gene soon
reveals himself to be a disturbed young man. He draws his energy from Finny, often
remarking that he only competes in athletics and plays games in order to gain Finny's
approval. In the first few chapters, Gene moves from praising Finny, practically gushing
over his awards and achievements, to instantly suspecting Finny of sabotaging his grades
and trying to ruin Gene's academic record. Yet Gene still needs Finny in a way, using
him to bolster his own sense of popularity and
acceptance.

After Finny returns to school following his
plummet from the tree, the two boys' relationship becomes closer than ever. Gene still
relies on Finny as his link to the rest of the boys; without Finny, Gene is quite
unpopular and doesn't seem to have many friends. But the dynamic of the relationship has
changed. Where once Finny seemed to be friends with Gene because he truly enjoyed his
company, after his fall Finny grows despondent. He uses Gene to live out his own dreams,
making him practice constantly and "train for the Olympics". Both of the boys know that
Gene will never go, but there seems to be a vicarious nature to the relationship, with
Finny living through Gene.

Through their
relationship, both boys seek to find themselves, building their true
identities. Finny knows himself throughout the book, and is comfortable
in his own skin (at least at first). After his fall, he becomes more withdrawn and tends
to hide his true feelings. It actually seems like he loses his identity as the novel
progresses. The innocence and general good nature that defined him early on is lost in
later chapters, as he continually deludes himself as to Gene's true intentions. Gene, on
the other hand, hides his true identity from Finny and the others through most of the
novel. Yet he reveals himself at several key points, such as his pushing Finny from the
tree. The entire novel becomes Gene's recollection of building his identity, culminating
in his return to Devon years later, where he is finally able to come to terms with what
he's done.