Captain Nemo and Aronnax act as foils for each other in the novel, meaning their juxtaposition reveals important aspects of each other’s characters. While Captain Nemo and Aronnax form a special bond because of their shared fascination with scientific advancement and the sea, they are different in critical ways. For example, Nemo has decided that being part of civilization is not worth the trouble—he would rather be isolated deep in the sea. Aronnax, on the other hand, as a professor at a prestigious institution, is deeply tied to society.
What turns Nemo and Aronnax into significant foils for each other is that their close relationship changes each of them. While Aronnax lives a respectable and stable life on land, he also expresses envy over Nemo’s “freedom” under the sea, such as in the scene when he meets Nemo (referring to him as “the Unknown”):
A flash of anger and disdain kindled in the eyes of the Unknown, and I had a glimpse of a terrible past in the life of this man. Not only had he put himself beyond the pale of human laws, but he had made himself independent of them, free in the strictest acceptation of the word, quite beyond their reach!
While it’s clear that Aronnax sees (and does not envy) Nemo’s “anger and disdain,” his declaration that Nemo is “free” is notable. It’s unlikely that Ned or Conseil would have described Nemo that way, revealing that there is something to Nemo’s lifestyle that Aronnax wants for himself.
While Aronnax’s proximity to Nemo makes Aronnax more desirous of an isolated, science-oriented life in a submarine, Nemo’s proximity to Aronnax opens him up emotionally. Though he never says so directly, Nemo comes to trust Aronnax as a companion and starts to share small details about his life, such as coming from a colonized nation and losing his family. Aronnax never feels he really knows Nemo, but it’s likely that, to Nemo, Aronnax was the closest he'd come to having a friend.
