I can understand how forgiveness is part of philosophy and theology, but I am having a hard time seeing how forgiveness can be placed into the scientific arena. After all, this is a highly abstract concept. How can it be studied scientifically?
Forgiveness is not the only abstract concept studied scientifically. The theme of justice also is abstract and has been part of the scientific landscape since at least 1932 when Jean Piaget began his work on children’s and adolescents’ understanding of justice. Gratitude is another abstract construct that is studied in the social sciences. We can study forgiveness because it is possible to define forgiveness in such a way as to make it concretely measurable. For example, we have the Enright Forgiveness Inventory which assesses the degree to which participants forgive one other person who was unfair to them. We categorize forgiving in this scale into 6 dimensions: the degree to which the participant 1) harbors negative thoughts and 2) negative feelings, and 3) exhibits negative behaviors toward the unjustly acting person; the degree to which the participant shows 4) positive thoughts and 5) positive feelings, and 6) exhibits positive behaviors toward the unjustly acting person. We are able to get a score for each participant. Science shows that when people go through forgiveness intervention programs, then their forgiveness scores on this scale tend to increase. People with high scores on this scale tend to show better mental and physical health than people who have very low scores on this forgiveness scale.
For additional information, see: Forgiveness Research.