As one a scholar and the other an athlete, Gene and Finny have been complementary selves — their abilities completing each other in friendship. After the fall, Finny determines to make the union of selves real in Gene, by training him to excel in sports as well as academics. For a superb athlete like Finny, the loss of physical ability represents an essential loss of self, a pain expressed in his uncharacteristically bitter remark, "I've suffered!" Yet Finny trains Gene with grace and good humor, delighting in his physical progress, generously sharing the dream of the 1944 Olympics. In fact, Finny trains Gene as enthusiastically as if Gene were a part of himself. Gene feels Finny's identification, and responds in turn by becoming, in his own way, a part of Finny.
The dramatic revelation of Gene's part in Finny's fall breaks the friendship temporarily, bringing about a nightmarish loss of self in Gene, but their reunion makes possible a new, more complete life. After Finny's death, Gene senses a new peace in himself, a self-confidence that enables him to cope with minor annoyances, like the condescension of Brinker's father, as well as great challenges, like service in the war.
By the end of the novel, Gene has fulfilled the earlier promise of the image in the mirror. He has killed his "enemy" — a narrow, fearful self — and filled himself with Finny's self-confidence and freedom. Gene has become a bigger and better self through friendship with his uncontrollable, unpredictable double, Finny.
