LitCharts assigns a color and icon to each theme in Moby-Dick, which you can use to track the themes throughout the work.
Limits of Knowledge
Fate and Free Will
Nature and Man
Race, Fellowship, and Enslavement
Madness
Religion
Summary
Analysis
Ishmael reports that the good luck of the Bachelor appeared to rub off on the Pequod, which spotted and killed four whales the next day. Ahab himself killed one of them, and from his whale boat Ishmael notes that Ahab looked out at the setting sun, and, noting that the sperm whale looked to that sun before dying, began rhapsodizing about the sperm whale’s “worship of fire,” and how the sperm whale then goes back into the sea to die. Ahab finds this sight greatly moving, and though it does not make him any happier, it does cause him to approach his hunt for Moby Dick with even greater energy and resolve.
Another instance wherein light is described, this time at the moment when the whale perishes. Ahab's belief that the whale worships fire is not fully explained—is he saying the whale worships what is the opposite of its experience (i.e. fire rather than the water of the ocean), is he suggesting that whales worship fire because they are devilish and connected to the fires of hell? Or because whale oil is used to make light? Or is there a connection here to the idea of Prometheus again, the bringer of fire?