Revenge is a primal force at the heart of conflict and justice--as ancient as humanity itself. It can be found in nearly all societies and, culturally, we are fascinated by it--as countless novels, dramas, films, and computer games attest. "Getting even" can restore the balance of relationships and bring order. It can fill the vacuum left by imperfect or unjust justice systems. It can rescue people trapped in oppressive conditions. But revenge can also get out of control; spirals of revenge are notoriously destructive and impervious to appeals for peace and forgiveness.

In this bold new...