The phrase “one plus one equals zero” shows up at several points in the novel, as does the symbol of two snakes eating each other. In a sense, these are two different versions of the same problem. As John sees it, the two snakes eating each other symbolize the unity of love—his love for Kathy specifically. At the same time, the image is gruesome, and foreshadows the anger and pain and mutual destruction that John and Kathy will cause each other. John sees his entire life as a version of the two snakes—he thinks that every action must be accompanied by an equal and opposite reaction. Thus, when he kills innocent people in Vietnam, he tries to “balance out” his murders by forging documents and enduring great pain and danger. One (John’s actions in Vietnam) plus one (John’s pain and lying) is meant to equal zero (total innocence). Yet, for much of the novel, it seems that one plus one never
equals zero. John tries to forget his guilt, but he can’t, and eventually, everyone in Minnesota knows that he participated in the massacre at Thuan Yen. Similarly, John’s relationship with Kathy isn’t the beautifully symmetric marriage he seems to want—John, the stronger and more persuasive partner, takes control of Kathy’s life and forces her to have an abortion, even though she wants children. And yet we’re also given some indications that one plus one can
equal zero. The narrator acknowledges that it’s possible that John and Kathy actually left Lake of the Woods together and learned to treat each other with love and mutual respect. There’s no proof that this happened, but it’s certainly possible. In the end, the image of the two snakes, which can be interpreted positively or negatively, stands for the events of the entire book. One can interpret the novel in an optimistic or a pessimistic light, depending on whether or not one believes that it’s possible to move past sin and guilt.