what to do with this rage? 

James points to Ishmael's self-proclaimed reasons for going out to sea. It is a basic and deep discontent, about to burst violence. Ahab is portrayed as someone who, to some extent similarly, carries disappointment and rage against civilized, orderly society. Different from Ishmael, Ahab did spend a lot of time out in the oceans. In fact, 40 years with very little time on shore. James takes this experience, coupled with the solitude of command and enhanced by losing his leg to MD, as the psychological factors leading to his madness.For James, both men, each in their own way, are a symptom of Western  Culture. Ahab, as the biblical allusion to his name calls, goes overboard in satisfying his revenge, doing as he wants without taking other people into consideration except as "mechanical" tools for getting his wish. Beyond the mastery of science and the promise of material gain, there is something else which this culture fails to satisfy. James sees Ahab as a mad totalitarian, just like Hitler or Stalin. They all use the building blocks of society, and using them to an evil end`- the sense of racial superiority supporting the nation state and its production (and therefore the mechanization of humans). Ahab is seen as both exploiting the tenants of culture to his own personal aim and as a product of this very culture. In a sense Ahab marks the borders of the system. Ismael too suffers from and is trying to work with what is given by culture (books) and by nature (his finding a soul mate in Qweequeg, or nature at large) and too suffers a crisis. The third in the triangle are the crewmen - bonded by their work and interdependency in doing it, they are happier than both Ishmael and Ahab, which are solitary. This leads to the main question for me, reading James - is this a psychological comment - it is best to find something to do and people to do it with? or is it a political statement saying that discontent and rage cannot be overcome within the realm of culture and that culture itself makes people, not only unhappy but even dangerous?