Ishmael asks the narrator about chapter two of the Leavers' story. He tries to get the narrator to think about what world change would look like, which brings him and the narrator to the issue of civilization. Ishmael helps the narrator understand that civilization isn't the problem, but the attitude civilized nations have toward the world is. The key is whether a civilized people see the world as belonging to them or as themselves as belonging to the world.
At this point, Ishmael reflects on his former students and informs the narrator that this is the point where most of them give up because they don't think such wide-scale change is possible. However, the narrator still remains inspired and wants to know what he can do to help change the world. Ishmael tells him he must be a teacher, for humans' minds must change before their actions will.
But before Ishmael sends the narrator out into the world to share the knowledge he's gained, he focuses on one last point. He reminds the narrator of the original metaphor of captivity he used to begin their lessons — that all members of Taker culture are imprisoned by a destructive, unfulfilling way of life. And, like any prison, it has ways of distracting inmates so they don't notice the conditions. The narrator sees that, for Takers, that distraction is consuming the world. Ishmael adds that it's also important to stay focused on breaking free of the prison, not simply on making conditions within the system more equitable for historically marginalized members (that is, non-white and non-male humans).
With that, Ishmael informs the narrator he's finished instructing him and goes to bed, though the narrator assures him he'll return tomorrow.
In the second half of Part 12, Quinn uses the ongoing theme of teaching and the metaphor of prison to help the narrator understand what must be done to save the world. Now that the narrator understands the historical circumstances leading up to the current state of the world, he's at a loss for what he's supposed to do about it. Ishmael suggests being a teacher. By having Ishmael, as the teacher, suggest his student become one, Quinn stresses the significance of student-teacher relationships as central to social change. Thus, Ishmael and the narrator are not only representative of an allegorical model of learning (similar to Socrates and his pupils, for instance) but are also a model for cultural change, for, as Ishmael suggests to the narrator, the only way to change people's actions is to start with their minds.
Furthermore, Quinn uses the metaphor of prison to help focus the narrator's role as a teacher. Recall that earlier in the novel, Ishmael explained that one of his motivations to educate himself was to better understand the idea of captivity. Ishmael returns to the idea of a prison to remind the narrator of the powerful ways Mother Culture hides the bars of her "prison." Thus, the narrator must use his understanding of this prison to help his fellow prisoners see what binds them to their ecologically destructive way of life. While the narrator is overwhelmed by his task as a teacher, Ishmael's provided him with useful metaphors, such as the prison, as well as the stories he's used in his instruction, to help the narrator reach others as he himself was reached.