To Ahab, killing the whale becomes the ultimate goal in his life, and this observation can also be expanded allegorically so that the whale represents everyone's goals. Furthermore, his vengeance against the whale is analogous to man's struggle against fate.

Readers could consider what exactly Ahab will do if he, in fact, succeeds in his quest: having accomplished his ultimate goal, what else is there left for him to do? Similarly, Melville may be implying that people in general need something to reach for in life, or that such a goal can destroy one if allowed to overtake all other concerns.

.. truly to enjoy bodily warmth, some small part of you must be cold, for there is no quality in this world that is not what it is merely by contrast

— Moby-Dick