At its most meaningful level, A Separate Peace presents a thoughtfully executed psychological study of its main character, Gene Forrester. Forrester’s sense of himself is an extremely dark and critical one, provoking feelings of insecurity particularly when he is in the company of Finny. Knowles explores the dual directions these feelings take: On one level, Forrester desires to get even (to outperform) Finny, he therefore resents Finny’s superior athletic skills. On another level, Forrester also wishes to be like Finny, to share his carefree, selfless attitudes and actions. In fact, Forrester clearly is most happy when he is at peace with Finny. At the end, however, Forrester’s dark side wins this psychological conflict; the final “peace” that is established between the two occurs after Forrester causes Finny’s fall, from which Finny never recovers. This action, in a psychological sense, eliminates Finny as Forrester’s rival and allows Forrester to feel less anxious about himself.
Yet less anxious does not mean good. At the conclusion of A Separate Peace— when Finny finally asks Forrester why he caused the fall—Forrester replies that he did not do it out of any personal hatred of Finny. Instead, Forrester is fighting himself—out of blindness and ignorance, as he himself admits—and Finny ultimately understands, before he dies, how he has been victimized by Forrester’s own psychological conflict. Essentially, then, Finny is simply an object (albeit a very important object) playing a part in Forrester’s personal battles. The finishing touch to Knowles’s psychological study occurs with Finny’s burial, when Forrester cannot cry because he has the feeling that part of himself is being buried with his friend. Thus, when Forrester eventually enlists and goes off to World War II, he does so without any genuine animosity. He has symbolically killed the enemy inside himself, and so he has no further need to find another person to symbolize his dark interior self.
Knowles’s exploration of how people are controlled by psychological forces which they do not understand far surpasses the war theme that is worked into A Separate Peace. This theme involves Forrester’s attempt to find a way to cope with World War II, a different kind of reality that awaits the Devon School boys after their school year. Different ways of dealing with the exterior world are offered by Finny (who ignores it, for as long as he can), Hadley (who approaches everything logically and reasonably), and Leper (whose romanticism fails to prepare him for the violence of enlistment and military service).
Once Forrester’s psychological battle with himself is over—it ends with Finny’s death—these themes are quickly dropped in A Separate Peace. Readers do not find out what happens to the secondary characters, nor does Knowles reveal what Forrester did during his military service. Forrester reveals that he did not do any fighting during the war, but that is all he has to say about it, and Knowles does not provide any information on Forrester’s life after the war, either. The basic theme of A Separate Peace concerns Forrester’s reconciliation with himself—the peace he establishes “separate” from the war—but the price he pays is a severe one since Forrester is far from being a happy or fulfilled individual at the novel’s end. The other themes of the novel— involving the other main characters and also the basic contrast between Forrester (as a Southerner) and Finny (as a typical Bostonian)—simply vanish at the novel’s end.