In A Separate Peace, by John Knowles, Gene is riddled with conflict for most of the novel. The story begins with an adult Gene looking back at his school days fifteen years ago at Devon, and he seems to have finally come to some peace. When he flashes back to Devon (which is nearly all of the novel), we learn what his conflicts were. One incident will serve as an example of both internal and external conflict as Gene struggles to mature.
Gene's conflicts all revolve around his roommate and friend, Finny. While Gene is the better student (though he has to work at his studies), Finny is a naturally gifted athlete with a gift for evading trouble with his charming personality and quirky beliefs. Finny is more interested in doing things than going to class or studying, and he imposes that on Gene--or at least this what Gene feels is happening. He assumes Finny is deliberately trying to sabotage Gene's studies.
Gene is often angry at Finny, though he does not particularly show it until Finny has convinced him to climb on a tree limb to jump, something Gene does not want to do. Finny's urging is a natural outpouring of his desire to share something with his friend; he assumes Gene likes what Finny likes because Gene has never told Finny, in any meaningful way, any differently. Gene jumps, but he hates doing it.
At the end of chapter four, the two of them are back on the tree limb. When they are there, Gene does something he will long regret and which will create conflict for him for a very long time:
I couldn’t stand this. We reached the others loitering around the base of the tree, and Phineas began exuberantly to throw off his clothes, delighted by the fading glow of the day, the challenge of the tree, the competitive tension of all of us. He lived and flourished in such moments. “Let’s go, you and me,” he called. A new idea struck him. “We’ll go together, a double jump! Neat, eh?... Come out a little way,” he said, “and then we’ll jump side by side.”
Holding firmly to the trunk, I took a step toward him, and then my knees bent and I jounced the limb. Finny, his balance gone, swung his head around to look at me for an instant with extreme interest, and then he tumbled sideways, broke through the little branches below and hit the bank with a sickening, unnatural thud. It was the first clumsy physical action I had ever seen him make. With unthinking sureness I moved out on the limb and jumped into the river, every trace of my fear of this forgotten.
Finny's leg is shattered in the fall, and Gene's conflicts intensify. Now he feels extreme guilt about what he did and what happened to Finny because of him. Gene also thinks, and rethinks, his assessment of Finny and wonders constantly if he has judged Finny by his own feelings and therefore found his friend guilty of something he was not. All of this remains an internal conflict for Gene because he and Finny are unable to speak about it openly.
The external conflicts which happen because Gene jounced the limb are also significant. While Finny is home recovering, Gene avoids participation in sports and changes nearly everything else he does. He had lived one way with Finny but lives another way now; when Finny returns, things are still strained and Gene's physical endeavors now have to represent both boys. This puts a significant pressure on Gene until Finny dies.
Gene struggles with the internal and the external ramifications of that one simple act for many years.