Forgiveness is the pardoning of others for their errors and misdeeds. Some ethical systems, such as Christianity, endorse unlimited forgiveness. Results of experiments with the iterated prisoner's dilemma suggest that the best strategy is tit-for-tat revenge followed by immediate forgiveness, with some occasional mercy randomly thrown in to disrupt destructive cycles of revenge that would otherwise result in mutually assured destruction. Historical analysis suggests that countries that allow discharge of debts in bankruptcy and for the bankrupts to then begin borrowing again have experienced positive outcomes. Murray Rothbard argues for a system of voluntary debt forgiveness.