Brinker Hadley is portrayed as a responsible, law-abiding student, who serves as Finny's foil in the novel. Unlike the spontaneous, carefree Finny, Brinker is one of Devon's top students who has an affinity for order and structure and is depicted as the rigid, obedient leader of his class.
Initially, Brinker is Finny's antithesis, and his character coincides with Devon's winter session. Brinker takes life very seriously, is an avid supporter of the war effort, and encourages Gene to enlist early in the army. Unlike Finny—who lives in a fantasy world and believes that the war does not exist—Brinker accepts the facts of life and attempts to get to the bottom of Finny's injury by investigating the accident.
Despite all of Brinker's patriotic enthusiasm and passion for joining the war, he quickly becomes disillusioned with the idea of fighting and ends up enlisting in the Coast Guard to avoid entering the conflict. Brinker's decision to abandon his earlier ideals depicts his growth and maturity, which are prominent themes explored in the novel.
Overall, Brinker Hadley's character serves as Finny's foil and his transformation into a jaded, cynical adolescent corresponds to the other characters' maturation and growth.