Quote 10
I finally identified this as the source of his disillusionment during the winter, this generalized, faintly self-pitying resentment against millions of people he did not know (13.35).
By rejecting World War II, Brinker has created his own private war – against his father and the men like him. Gene's point that we all choose our enemies is reiterated here.
Quote 11
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 suspended all but changed nothing, that you couldn't make yourself over between dawn and dusk. Phineas however did not believe this. I'm sure that he looked down at his leg every morning first thing, as soon as he remembered it, to see if it had not been totally restored while he slept (8.14).
Gene has moved on into this new Winter Session, a time of maturity and growth. Finny is absent, so he misses the transition. When he comes back to Devon, he's still in Summer-mode.
Quote 12
Phineas was a poor deceiver, having had no practice (8.72).
Finny remains the epitome of youthful naiveté, even after his injury.