Forgiveness is never going to be easy," wrote Sister Helen Prejean, of families who were struggling to relinquish their feelings of revenge and bitterness toward murderers who had killed a family member, especially a child. "Each day it must be prayed for and struggled for and won."

In Dead Man Walking, Sister Prejean argues forcibly that forgiveness is the only civilized alternative to the state-sanctioned revenge of capital punishment. While her treatise against the death penalty is fortified with arguments based on law and reason, there is little to explain how the families she came to know could learn to forgive—and why some of them could not—the most unforgivable crimes.

As always, it would seem, forgiveness must remain a mystery, an affair of the spirit, and impervious to inquiry.

But now, scientists of many stripes want to know what forgiveness is, how it happens, and what its effects are on human health and relationships. Research and interest in forgiveness appears to be exploding. A nonprofit corporation for generating dollars for researching the nature and effects of forgiveness has been established (see box), and researchers from a variety of disciplines have joined the effort.

"Until recently, the tools of science have not been employed to investigate forgiveness," said Everett Worthington Jr., Ph.D., a clinical psychologist at the Virginia Commonwealth University. "It has only been since the mid-1980s that scientific researchers in health, biology, basic and clinical psychology, sociology, and political science have begun to establish a beachhead of scientific understanding of forgiveness. These proposals have potential to reveal the profound value of the multiple dimensions of forgiveness in our lives."

Worthington and others in the field of forgiveness research say it has enormous implications for psychiatrists and their patients. But it is also being applied in efforts to reconcile groups of people, races, and nations.

In one respect, the phenomenon dovetails with the movement to integrate medicine and spirituality; it has been furthered significantly by the John Templeton Foundation, a nonprofit group interested in the interface between religion, spirituality, and health. On another level it is an extension of efforts by researchers over many decades to measure and quantify cognitive and affective states and to link them to physiological functioning.

The field had its beginnings in reports published by therapists working with couples around issues of reconciliation. Worthington said it was in the 1980s that he began to pay attention to the radical influence of forgiveness—or of the inability to forgive—in determining whether couples could reconcile bitter differences.

He confesses to having "no impulse control" when it comes to research: "If it moves, I want to measure it and write about it," he said.

In tackling forgiveness, it would seem that he has entered a realm where measurement would be all but impossible. Nonetheless, Worthington said that remarkable strides have been made in conceptualizing forgiveness and quantifying its effects on individuals and on relationships. He has published basic and interventional studies looking at how forgiveness affects physical and emotional functioning. While much remains to be learned, some fundamentals are being established, he believes.

Personality types appear to be related to the capacity to forgive or not to forgive. The traits of anger, rumination, and neuroticism—"the usual suspects," Worthington said—appear to predispose individuals to being unforgiving. The converse of those traits—agreeableness, generosity, and empathy—is likely to predispose one to let go of grudges.

But what exactly is forgiveness? Worthington believes it is an essentially affective transformation that can be profound and sudden, or painstaking and incremental. "I look at forgiveness as an emotional replacement of unforgiving feelings with positive emotions, such as love, empathy, or compassion," Worthington said.

It is a concept that draws on the work of neuropsychologists looking at the way feelings early in life become "embodied" through the neurochemical activity of the brain, especially the prefrontal cortex, believed to be the seat of "working memory." In theory, it works like this: the body produces neurotransmitters that light up different parts of the brain in response to any experience—say, a slight, an insult, or a violation—producing musculature patterns and other bodily sensations specific to different emotions. Those sensations are fed into the working memory of the brain, which "labels" the experience with the newly "embodied" feeling. Later, when any similar slight or an insult is experienced, the old embodied emotion will be reproduced.

Worthington said that the replacement of unforgiving emotions with forgiving ones can occur within a continuum between two extremes. At one extreme is the painstaking effort to "chip away" at old, embodied responses, as might be accomplished in therapy when a patient works through old memories, learning to reinterpret them. In time, new experiences of hurt or insult will produce different emotional responses.

The other, much rarer, form of forgiveness occurs when a victim spontaneously experiences a powerful reversal of embodied emotion—hormones, muscles, and neurotransmitters all working suddenly and mysteriously in ways never before experienced. It is this latter experience that some outside the scientific laboratory have called "grace."

And it is here, perhaps, where scientists and the mental health community greet the religious and spiritual, in whose domain forgiveness has traditionally resided.

Clark Aist, Ph.D., who is a chaplain at St. Elizabeths Hospital in Washington, D.C., and serves as a consulting member to APA’s Committee on Religion and Psychiatry, said that psychiatry has contributed much to furthering the role of forgiveness in treatment—while perhaps using different terminology—and the understanding of the delicate nature of that internal phenomenon.

He recalled a professional conference in 1965 when a prominent psychiatrist was presenting a case history in which a patient was described as being in need of a forgiving word from the therapist. "And yet," Aist quoted the speaker, "it would have been inappropriate, because the patient wasn’t yet ready for it."

The moral to the story, Aist said, is that "forgiveness is not a facile tool."

For Aist, the distinguishing mark of forgiveness is the ability to recognize in one’s victimizer one’s own capacity to victimize and one’s own need for forgiveness. Hence, the wayward spouse, the abusive partner, even the murderer, can be forgiven when an individual recognizes his or her capacity for infidelity, abuse, and murder.

And therein, he suggested, lies the great emancipating power of forgiveness in human affairs and its terrible difficulty as a concept in psychiatric treatment. It is especially perilous for the therapist, Aist said, because it can easily be misused to "blame the victim" and thereby to repeat the victimization.

But while scientists seek to locate forgiveness in neurotransmitters, for Aist the ability of one tormented individual to relinquish his fury is only a pale reflection of the need for a more encompassing mercy. And the capacity to recognize oneself in one’s tormentors—to achieve a release from old, embodied emotional responses—may ultimately be impossible through human efforts alone, he observed.

It is a lesson that has been reinforced working in a place where the difficulty of forgiveness, and the importance of trying, is a staple of everyday therapy. "The most seriously mentally ill are liable to have a litany of offenses that have been committed against them—by parents, hospital staff, and friends," he said. "These grievances come up again and again, and each time we have to work on forgiveness until we come back to where we had been before. But this is a place where the differences between the so-called normal and pathological come together and dissolve. We are all so broken."