Through the mid-twentieth century, academic treatments of forgiveness were largely theologically based. The latter part of the century saw the start of a secular discussion of forgiveness within analytic philosophy. The topic provides rich ground for philosophical reflection.

Participants in the discussion often focus on three issues: what forgiveness is, how it is accomplished, and when it is justified. Regarding the first, many appropriate Bishop Butler's claim that forgiveness is the overcoming of resentment. It is widely thought to be accomplished through compassion, perhaps by an imaginative process. The question of justification raises interesting issues about whether forgiveness can be required or whether it is always supererogatory.

There is, however, a prior question of considerable philosophical interest: How is forgiveness, so understood, even possible? Most would agree that not just any elimination of resentment counts as forgiving. You could not forgive by simply taking a pill that rendered...