Many religions and much religious thought would have us believe that good and evil have as their source attributes that resides outside the confines of the human brain. This viewpoint, by its nature, establishes a duality in nature. From this perspective, good has its origins in a benevolent creator and evil is often imputed to stem from the workings of a malevolent force or being such as the devil. If such a duality exists, this construct proposes an intrinsic dilemma – if the creator fashioned humans in his own image, why is there evil in the first place? To help assuage this apparent contradiction, theologians have posited the concept of free will. In other words, the individual is free to choose what course to pursue in life, and can, therefore, be held personally accountable for those choices – hence the concepts of heaven and hell.
Our system of jurisprudence bases the punishment of those who indulge in criminal behavior on the presumption of personal responsibility and the idea of free will. This is a fundamental aspect of the system and is used to justify all manner of retribution, including murder.
I believe that this thinking is essentially erroneous. The modern science of neurobiology, especially in regards to the neuronal structure of the human brain has clearly established the role of particular circuits that are involved in various aspects of human behavior. One area of the brain that has been studied in some detail is that involved in pleasure. In this regard, scientific studies of drug addiction and its effect on the brain have revealed the involvement of the pleasure and reward circuits – drug abuse seems to lead to changes in the structure of the brain in these areas.
It would not be unreasonable to speculate that brain activity is responsible for that set of behaviors that we attribute to goodness. In humanity's early history, benevolent and compassionate behavior of individuals towards fellow members of the local community – tribe – was essential for continued survival of the group and the successful living of individuals within that group. In other words, goodness is an intrinsic aspect of human behavior. If there is, in fact, a "goodness circuit" within the neuronal structure of the human brain, then the anomalous and destructive behavior that is attributed to evil may actually be explained by a disruption and change in this circuit. Traumatic experiences during childhood may, like the example given of drug addiction, disrupt, damage or interfere with this goodness circuit.
Studies of the brains of psychopaths and sociopaths suggest, in fact, discernable changes in brain function and chemistry. If human behavior ascribed to what is considered good and that related to what is regarded as evil is directly dependent upon brain activity and function, then the concepts of good and evil must, necessarily be re-evaluated along with the notion of free will.