Pierre Aronnax is a professor and scientist. As the novel begins, he is single-mindedly obsessed with his scientific studies as a marine biologist. The Nautilus gives him unprecedented access to the ocean and its environs, and he is thrilled at the opportunity for study that this affords him.
Aronnax is the narrator of the story, and he struggles between honoring his scientific pursuits and living in a humane way. He can be arrogant, as his name implies, as well as class-bound and snobbish, and he likes to drop obscure references that the average person might not understand. He relies on what he reads rather than actual experience of life to make decisions, making him an opposite, or foil, to Ned Land.
Paradoxically, Aronnax initially feels so freed by this opportunity to study the sea that he is blind to the loss of liberty Captain Nemo imposes. Even when he realizes it and knows he should follow Land in attempting to break free, the research the ship affords him makes him hesitate. It is only after he witnesses Nemo's inhumanity that he begins to change and grow, making the decision to trust the experience of his senses and to value humane behavior over scientific study and discovery.