John Knowles explores many themes in his novel, A Separate Peace; three of the most predominant themes throughout the novel are warfare, identity, and jealousy.
- Search for Identity-- Gene struggles to define himself outside of Finny in A Separate Peace. He wants to establish his own identity, but his close rivalry and friendship with Finny makes Gene feel conflicted as to who he really is. Gene often thinks of himself in terms of what he can do and how he can excel--if he could be the top student, if he could be the best athlete--by the end of the novel, Gene comes to realize that his own identity is linked much more closely to the kind of man he wishes he could be.
- Warfare-- Set during World War II, battles, war, and enlisting figure heavily in many of the boys' minds at school, but Knowles also brings in an element of personal warfare amongst the boys: for example, Gene's private war with Finny, who is largely unaware of the conflict.
Everyone has a moment in history which belongs particularly to him. It is the moment when his emotions achieve their most powerful sway over him, and afterward when you say to this person "the world today" or "life" or "reality" he will assume that you mean this moment, even if it is fifty years past. The world, through his unleashed emotions, imprinted itself upon him, and he carries the stamp of that passing moment forever" (Ch. 3).
- Gene's "moment" in the quote above concerns Finny, whom Gene begins to see as an enemy who threatens to overshadow his success at school.
- Jealousy-- Jealousy figures largely in Gene's actions and thoughts. He is extremely jealous of Finny's general likeability, talent for benign rule-breaking, and athletic ability.
"I was beginning to see that Phineas could get away with anything. I couldn't help envying him that a little, which was perfectly normal. There was no harm in envying even your best friend a little" (Chapter 2).
- Ultimately, Gene's jealousy deepens into a hatred for his once good friend, poisoning the way Gene sees and interacts with Finny. The destructive quality of Gene's jealousy leads him to make choices that have far-reaching negative consequences.