In chapter 4 and 5, specific aspects of Gene's characterization emerge. One of these elements is that Gene vacillates over some critical moments. Essentially, Gene vacillates over his relationship with Finny. He undergoes some significant change in terms of his perception and self- perception. In chapter 4, Gene has to retreat from his original position that Finny wants to academically undermine him. Through an exchange between both of them, it is clear that Finny perceives Gene to academics as he is to sports. As a result, Gene vacillates over his antagonism towards Finny, and is convinced that he is uncertain about "whom (he) hate(s) and who hate(s) (him)." The lack of clarity in his own world and his perceptions about Finny give him some cause for uncertainty and indecision.
From this moment of ambiguity, greater cause for Gene's vacillation emerges. The "accident" at the tree might itself represent a moment of vacillation or indecision. Why Gene jostled the tree branch on which Finny was standing becomes an instant where he vacillates, unable to clearly reason why he did. Gene's vacillation between friend and enemy causes a massive change in Finny's life. Afterwards, Gene vacillates between regret and support when he has to visit a physically challenged Finny. He has to put on a "brave front" and his vacillation between this persona and what he truly feels and wants to say in front of Finny creates another instant of vacillation. Finally, when Finny is discharged, Gene tells the truth to Finny, thinking that it is the best approach to take. However, the very idea that his best friend would want to do something so willfully malicious and painful causes "an even deeper injury that what (he) had done before." This causes vacillation in Gene. He is not entirely certain what he needs to do or what he should do. In chapters 4 and 5, Gene's vacillation, of indecision, is critical to the arc of his development and the plot's structure.