@Pythagorean,
Contrast this with the later dialogue "in the cabin":
“Devils! Dost thou then so much as dare to critically think of me?- On deck!”
“Nay, sir, not yet; I do entreat. And I do dare, sir- to be forbearing! Shall we not understand each other better than hitherto, Captain Ahab?”
Ahab seized a loaded musket from the rack (forming part of most South-Sea-men’s cabin furniture), and pointing it towards Starbuck, exclaimed: “There is one God that is Lord over the earth, and one Captain that is lord over the Pequod.- On deck!”
For an instant in the flashing eyes of the mate, and his fiery cheeks, you would have almost thought that he had really received the blaze of the levelled tube. But, mastering his emotion, he half calmly rose, and as he quitted the cabin, paused for an instant and said: “Thou hast outraged, not insulted me, sir; but for that I ask thee not to beware of Starbuck; thou wouldst but laugh; but let Ahab beware of Ahab; beware of thyself, old man.”
“He waxes brave, but nevertheless obeys; most careful bravery that!” murmured Ahab, as Starbuck disappeared. “What’s that he said- Ahab beware of Ahab- there’s something there!”
Shortly thereafter, on deck, Ahab says to Starbuck, before giving to the crew the orders Starbuck requested but Ahab had violently resisted, "“Thou art but too good a fellow, Starbuck,” he said lowly to the mate . . . .
Haunted, driven Ahab, of course, is not so "good a fellow," but one who would "strike the sun if it insulted me."