Finny admits that he chose not to believe in the war because he couldn't participate in it.
Finny is the narrator in John Knowles' book ' A Separate Peace'. The book explores morality, patriotism and loss of innocence during the World War II period.
In Chapter 8 Finny tells his roommate Gene that the 'war stuff' was a myth. His theory is that the war is 'fake' and a conspiracy done by old men who don't want the young to take away their jobs. He chooses to conduct himself as though there is no war going on and insists on training Gene for the 1944 Olympics.
Finn later confesses to Gene that he really knew there was a war but he denied the knowledge. Due to his injury, he could not be drafted. He contacted many branches of the army and begged them to be taken to fight but he was dismissed every time. He is bitter and disappointed and he is masking his feelings with his denial of the existing war.