Chapter xv and Chapter xvi are largely an exploration of suffering. In Chapter xv, Joe feels himself begin to go insane, as he continues tapping during all waking hours and tries to understand why he is not being heard. His panic quickly advances to paranoia as he figures out the problem: it is not that no one understands the larger significance of his tapping, but that no one wants to understand the larger significance. Joe's contextualization of his plight in terms of historical slavery is, in one sense, a way for him to alleviate his panicked loneliness; he is not alone, as others throughout history have experienced the bodily and mental subjugation he is experiencing now. However, Joe then asserts that his plight is actually worse than theirs, which leaves him alone in his suffering once again.
Chapter xv also reintroduces political concerns into the novel. Joe's contextualization of his plight in terms of historical slavery adds a political dimension to his suffering—as with the slaves throughout history, someone captured and used Joe, probably for profit, in one sense or another. Joe compares World War I to games at the Coliseum in ancient Rome, in which slaves were forced to fight each other for the pleasure of spectators. Chapter xv continues the "us" versus "them" dynamics we have seen before; when a doctor comes into the room and sedates Joe, Joe sees this act within those dynamics as well. "Us" is, by various names, the slaves, the little guys; "them" continues to be those who organize or profit by war, and now also the medical establishment, probably a military hospital. Joe's current helpless state—in which the hospital staff cannot conceive that he might be communicating, and thus further oppresses him—allows him to begin to understand that he was taken advantage of far before his injury. He has been a pawn since his initial entry into the war.
Chapter xvi portrays Joe in a drugged state, yet the chapter continues to deal with the suffering explored in Chapter xv. Joe's dream, like his mental argument in Chapter xv, proceeds from his identification with and incorporation into a group of others who are similar; it ends with Joe's alienation from that group. Here, the group consists of the men leaving the train station to go to war. It relates back to Joe's memory of the scene in Chapter iii, though here the men know that they will die. This knowledge of imminent death brings them together; they receive a visit from Christ, a fellow sufferer, who appears much like themselves. Suddenly, however, one of the men notes that Joe will not actually die in the war. The men let him remain with the group, acknowledging that his fate will be worse than death. However, Joe himself decides he does not belong. He leaves the men in search of Christ, whom he hopes will understand and aid his suffering. In these chapters, Joe's alienation stems not from his inability to communicate with the rest of the world, but from the fact that he is categorically different from even those who have suffered badly.