Finny's outlook on life shaped his reactions to every situation. He revelled in seizing the moment and exploiting every opportunity as it was happening, without analyzing or digging for hidden meanings.
During the snowball fight, which Finny had organized, he was a recruiter and leader for one side of the fight ("You're on our side, even if you do have a lousy aim. We need somebody else. Even you."); he switched to the other side in order to confuse and prolong the battle; and "with a steadily widening grin, he was driven beneath a blizzard of snowballs" as everyone else turned against him at the end of the fight.
Phineas looked at the world with an innocence that prevented him from believing in anger or hate or war. He
created an atmosphere...,a way of sizing up the world with erratic and entirely personal reservations, letting its rocklike facts sift through and be accepted only a little at a time, only as much as he could assimilate without a sense of chaos and loss.
The joy of the competition, the physical exertion of the activity, the excitement of showing your abilities and using them well - those were the only things that were important to Finny. He didn't care to consider or face the possibilities of real anger or hatred or jealousy, so the ideas of fighting or of war were beyond his realm of acceptance.