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 observes that, when the quadrant was working, Ahab did not feel it necessary to use the “log and line,” or a bob attached to a rope that is thrown out of the boat at set intervals, as a way of measuring the ship’s progress and speed over time. Now, though, Ahab orders two crewmembers to throw out the bob, even though it is nearly broken from the heat and of the long voyage. The crewmembers say this to Ahab, who tells them to throw it over anyway, and when the bob breaks, Ahab realizes that he has broken most of his means of locating the ship (the log, the needle, and the quadrant). Ahab asks Pip to come help him, but Pip responds with nonsense spoken in his customary tones of bizarre sing-song. Ahab comments that Pip has touched his "inmost center", and tells Pip to come with him into his cabin. Pip responds that he and Ahab have between them a “man-rope; something that weak souls may hold by.” The crew looks on, feeling that Ahab and Pip are both equally insane.
With the loss of the log and the line, Ahab realizes that all standard means of navigation are now lost to the ship. That Ahab then reaches out to Pip is interesting—in the absence of science he reaches out to prophecy as something that could direct him. But Pip’s prophecies and bizarre words are immensely difficult to interpret exactly. Yet at the same time, in their senselessness, they seem to capture the chaos and strandedness of the ship, which is now entirely in the grip of fate and Ahab's monomania. Ahab's tenderness toward Pip is a humanizing moment, as he seems to take Pip almost as a son. The two of them are almost total opposites—white and black; powerful and weak; knowledgeable and innocent; and yet they have a human connection between them (once again characterized by a rope). Yet their connection seems to be one founded on madness.