Ahab's quest is significant for a variety of reasons. Ahab's quest shows the consuming nature of revenge. Ahab is singular in his focus. He is almost epic in how he sees his purpose as revenge against that which had done him wrong. When Ahab speaks, this significance is amplified:
Aye, aye! and I’ll chase him round Good Hope, and round the Horn, and round the Norway Maelstrom, and round perdition’s flames before I give him up. And this is what ye have shipped for, men! to chase that white whale on both sides of land, and over all sides of earth, till he spouts black blood and rolls fin out.
There is a perceived absolutism to Ahab's quest. It defines his very being. It shows the lengths to which vengeance can overtake the human soul. This certainty is his focus, and it is something that makes both his quest and his characterization important: "There was an infinity of firmest fortitude, a determinate, unsurrenderable wilfulness, in the fixed and fearless, forward dedication of that glance.” For Melville, the "fortitude" that Ahab displays is what makes him so significant and so meaningful to the narrative.
For Melville, the consuming nature of Ahab's quest is significant. It precludes any balance or sense of reason within him. Rather, it is seen as "fixed" and binding. Melville suggests that vengeance as a means to appropriate reality prevents a full actualization of the human being. It takes away from such development. Ahab's words become evidence of this:
To me, the white whale is that wall, shoved near to me. Sometimes I think there’s naught beyond. But ’tis enough. He tasks me; he heaps me; I see in him outrageous strength, with an inscrutable malice sinewing it. That inscrutable thing is chiefly what I hate; and be the white whale agent, or be the white whale principal, I will wreak that hate upon him. Talk not to me of blasphemy, man; I’d strike the sun if it insulted me.
The significance of Ahab's quest lies in what it does to him. Ahab shows that revenge has made him think that "there's naught beyond." He has become driven by the need to "strike" that which lies beyond his reach. While the whale might represent “Retribution, swift vengeance, eternal malice were in his whole aspect.…," this is also telling as to how Ahab has become as a result of his quest.
Ahab has lost any semblance or perspective of understanding. He has become that which is no longer in control. Anger in the form of revenge is in control of Ahab. He is no longer in control of it. To this extent, Melville shows Ahab's quest as significant because it is a reminder of how easily the individual can lose their way when matters of pride, revenge, and anger converge within the human soul. This significance is illuminated in the madness of Ahab, himself: "I am madness maddened!” Revenge has become "a vulture feeds upon that heart forever; that vulture the very creature he creates.” This is where Ahab's quest is significant and where it is meaningful. It is a statement of what human beings can be when susceptible to revenge, anger, and unchecked emotions.
Critic Karen Tanguma calls both Ishmael and Ahab "Old World Adams": solitary men who seek the truth on the spiritual depth of the sea, the world and teacher to Herman Melville, who has spent most of his life upon it. As such, Tanguma writes,
Ishmael suffered into knowledge and spiritual rebirth and returned to the human race. Melville enhanced Ahab's unfortunate fall, through the novel's dark elements of evil, fear, and dark history....
In this vast allegorical novel, while Ishmael emerges and grows in wisdom and spiritual knowledge as the sole survivor of the Pequod, he is "escaped alone to tell thee" [Job 1:16] his tale because Ahab ("tragic Adam") becomes entrapped in his dark rage--"oh, lonely death on lonely life"--and he denies God as he seeks to kill the white symbol of spiritual power,
"Towards thee I roll, thou all-destroying but unconquering whale; to the last I grapple with thee; form hell's heart I stab at thee; for hate's sake i spit my last breath at thee."
Ahab is wrapped in the shroud of the sea, having blasphemed Nature and God. Ahab's quest has been one to find meaning, but he has found none.