How does the theme of wisdom apply to "A Separate Peace"?John Knowles's "A Separate Peace"

The theme of wisdom is very relevant to "A Separate Peace." As the older Gene returns to Devon School and reviews his life there, he recalls his early belief that Finny wishes to keep him from doing well at Devon because of jealousy for his intelligence. Gene's misinterpretation of Finny's nature leads him to shake the limb that causes Finny to fall and break his leg.  But, still Gene is "stopped by that level of feeling, deeper than thought, which contains the truth," and Gene cannot accept the fact that he has understands at the end of Chapter 4: Finney

had never been jealous of me for a second.  Now I knew that there never was and never could have been any rivalry between us. I was not of the same quality as he.

That he is not of the "same quality" as Finney bothers Gene.  Still, he follows Finney's instructions that he play sports for him; Gene, then, says that he

lost part of [himself] to him then and a soaring sense of freedom revealed that this must have been my purpose from the first:  to become a part of Phineas.

With this new life, substituting for Phineas, Gene

welcomed each new day as though it were a new life, where all past failures and problems were erased, and all future possibilities and joys open and available, to be achieved probably before night fell again. 

However, Gene realizes that he can not take Finny's role without Finny's losing:

Now in this winter of snow and crutches with Phineas, I began to know that each morning reasserted the problems of the night before, that sleep suspened all but changed nothing, that you couldn't make yourself over between dawn and dusk.  Phineas, however, did not believe this.

After the accident, Phineas now needs Gene. After Brinker holds his trial, and Finny rushes out, rebreaking his leg, Gene has that moment of truth, an "ephiphany," as he lies on the ground staring up at the night sky:

The old trees surrounding it all were intensely meaningful...and all the other building and all the people there were intensely real, wildly alive and totally meaningful, and I alone was a dream, a figment which had never really touched anything.  I felt that I was not, never had been and never would be a living part of this overpoweringly solid and deeply meaningful world around me.

Clearly, there is an insight into life that Gene gradually arrives at:  "Phineas in the Infirmary, and [him]self responsible. Later in this Chapter 12, Gene apologizes to Finny, explaining why he jounced the limb,

it was just some ignorance inside me, some crazy thing inside me, something blind, that's all it was.

Gene realizes, too, that not just private wars, but world wars

were not made by generations and their special stupidities, but that wars were made instead by something ignorant in the heart.

In his increasing wisdom aided by time, Gene realizes that "only Phineas never was afraid, only Phineas never hated anyone."  Confronted with Phineas's ingenuous nature, Gene could not imagine that anyone would not be competitive and jealous.  It takes his engagement in World War II "where he never killed anybody" for Gene to see in hindsight that, in comparison with his participation in the war, he "was on active duty all my time at school; I killed my enemy there."