Melville tells us that more than any other sailor, the whaleman is prone to superstition -- and a white bull whale that has killed, but cannot be killed, becomes the subject of an unreasoning, fearful dread of the supernatural in the whaleman's imagination. "The whale fishery surpasses every other sort of maritime life in the wonderfulness and fearfulness of the rumors which sometimes circulate there. One of the wild suggestings linked with the White Whale was the unearthly conceit that Moby Dick was ubiquitous; that he had actually been encountered in opposite latitudes at one and the same instant of time." This "conceit" developed into the belief that Moby Dick was immortal. [As for the unusual term "moby", some contend that it is a corruption of "mocha", as in Mocha Dick, a celebrated devil of a whale encountered off the Pacific coast of South America. But another likelihood is that "moby" is short for "morby" -- short for morbid. Ahab, mutilated by the white whale, will later complain that "no one can raise him moby dick" .]
On top of all of this, the real Moby Dick was known to attack his hunters on purpose in their whaleboats, smashing the boats to bits with his flukes [tail] and his massive head, and then to vengefully mutilate and kill them as they floundered in the water. An encounter with this particular Leviathan resulted in a "stove boat" for sure -- not a dead whale. [Far beyond the misdemeanor of staving in a whaleboat, enraged bull sperm whales were known to commit the felony of staving in the mother ship itself. More of the Nantucket whaleship Essex later.]
On one defining occasion, a Nantucket captain named Ahab, not about to suffer three stove boats, swam at Moby Dick with a knife in his teeth, and tried to stab the behemoth to death. As if to taunt this puny mortal, the whale simply amputated one of Ahab's legs, succeeding in driving the old man morbid-crazy. "The White Whale swam before him as the monomaniac incarnation of all those malicious agencies which some deep men feel eating them. All that maddens and torments, all that stirs up the lees of things, all the subtle demonisms of life and evil were personified, to crazy Ahab, in Moby Dick. Forced to return home, Ahab and anguish lay stretched in delirium together in one hammock, rounding the howling Cape in the winter. On the homeward voyage in a strait-jacket, the final MONOMANIA seized his torn body and gashed SOUL." Back on Nantucket, far from distrusting his fitness for another whaling voyage, "the calculating people of that prudent isle" decided "he was all the better qualified for a pursuit so full of rage as the bloody hunt of whales."
"But Ahab had purposely sailed on the present voyage with the one, only, and all-engrossing object of hunting the White Whale. Had any one of his old acquaintances but half dreamed of this, how soon would their righteous souls have wrenched the ship from such a fiendish man! They were bent on profit; he was bent on revenge."
All men tragically great are made so through a certain morbidness, says Melville.