How has Leper changed in Chapter 10 of A Separate Peace? What is a Section Eight discharge? Why didn't Leper want it?
Leper is a psychological mess. He had always been different, but he had always been impeccably friendly, courteous, and reserved. When Gene goes to visit him at his house, however, he is bitter, ranting, and rude. His speech is harsh and laced with curse words, and he seems to have no filter for what he says. Gene notes with dismay that "the careful politeness" that had always characterized Leper is gone, and as Leper describes the horrors he sees in his mind, Gene realizes that "none of this could have been said by the Leper of the beaver dam," the Leper of before the enlistment. Leper had been completely unable to handle the realities of military life. His mental state had deteriorated to the point that the army had been about to release him on a Section Eight discharge.
In Leper's words, a Section Eight discharge is "for the nuts in the service, the psychos, the Funny Farm candidates." It is worse than a dishonorable discharge because it marks an individual for life. Leper says that he would not ever be able to get a job if he had taken the Section Eight discharge, and that people would always look upon him with disgust. In his words, "you're screwed for life, that's what a Section Eight discharge means" (Chapter 10).
When Gene visits Elwin "Leper" Lepellier, Leper is at home in Vermont and has returned from his short service in the army. Instead of being the nature-loving and timid boy he was, Leper has become defensive and angry. He was given a Section Eight discharge, which is a dishonorable discharge from the army based on psychiatric grounds. He doesn't want this type of discharge, as he thinks he will have to show it to future employers, who will never hire him (they will think he is too crazy to work).
Leper shows a mean streak during Gene's visit. He tells Gene “oh they’ve got you all right,” referring to the army. Then he lets Gene know that he thinks Gene is a savage who deliberately knocked Finny out of the tree. When Gene and Leper trek across the winter Vermont landscape, Leper is more himself and tells Gene that the army really made him nervous, as he slept through everything and then couldn't sleep at night or eat in the mess hall.