In Chapter 9 of "A Separate Peace, there may be several symbolic meanings attached to the burning of the copy of the Iliad in order to begin the games of "The Devon Winter Carnival." Being set in the time of World War II, Gene, the narrator, remarks that Phineas
drew me increasingly away from the Butt Room crowd, away from Brinker and Chet and all other friends, into a world inhabited by just himself and me, where there was no war at all.
So on Carnival day, "this day of high illegal competitiveness," Phineas pulls Gene away from reality, its wars, and rules. Thus, the burning of the Iliad symbolizes Phineas's desire to diminish the importance of war to Gene.
Another meaning of the Iliad's burning may be that this classic Greek novel, reflective of both the people who instituted the Olympic games and the chronicling of the Trojan War, is destroyed to symbolize the boys' rebellion against the War.
Finally, Phineas may wish to symbolize his liberation from the setting of his life. The book's burning and the winter carnival symbolize escape from reality:
his own inner joy at life for a moment a it should be, as it was meant to be in his nature. Phineas recaptured that magic gift for existing primarily in space, ....It was his wildes demonstration of himself, of himself in the kind of worl he loved; it was his choreography of peace.
Gene, too says that he feels exhilirated, with "a separate peace":
It wasn't the cider which made me surpass myself, it was this libertion we had torn from the gray encroachments of 1943, the escape we had concocted, this afternoon of mementary, illusory, special and separate peace.