"Good" and "evil" are moral values that are defined in a metaphysical context of faith. In Christianity, "good" means that which is of God, and "evil" is that which is opposed to him; in fact, the words "good" and "god" have the same etymological root.
"Good" and "evil" are things we know not just with our minds or even our hearts, but with our spirits. A Christian would say that since they are spiritual concepts, they can never be defined scientifically.
What makes something evil?
What if you are a secular scientist who is nevertheless aware of the idea and existence of evil? You might do what artificial intelligence researcher Selmer Bringsjord, of Rensselaer Polytechnic Institute, did: try to define this non-scientific concept in scientific terms. Here are the criteria he came up with to define an evil person:
- The person must have planned or attempted (with or without success) to do something with the explicit intention of causing harm or pain to others.
- He or she must have done it without prompting, that is, independent of peer pressure.
- The person's reason for doing the morally bad thing must be either "incoherent," or the person must regard the harm caused as something good.
- The act must be a grave matter — i.e., a serious wrong — or considered by the person to be a grave matter.
- The person must be aware that it is a grave matter — ignorance is an affirmative defense with mortal sins.
- The person must give full consent to the act without being coerced against his or her will.
Evil deeds v. evil people
One major discrepancy between Bringsjord's criteria and Christian views of evil stands out: Bringsjord is defining an evil person, while Christians talk only about evil acts. Traditional Christianity holds that all of us suffer from a fallen nature, so we are all inclined toward evil deeds; but because we were created in God's image to be with him, and because any sin can be forgiven, no human can be essentially evil. Thus the Church speaks of sins, not of evil people.
Why define evil with a secular world view?
What is Bringsjord's purpose behind defining evil people? He even created a computer model of a perfectly evil person — but to what end?
His model is part of a larger program of developing simulations for human behavior. If you have a wholly secular, materialistic worldview, and regard human behavior as the result of scientifically definable brain activities, perfect simulations are theoretically possible.
I would argue that Bringsjord is barking up the wrong tree. Moral decision making is dependent on the spirit, not just the organic brain. Computerized copies can never be more than approximations based on outward appearance; they will never capture the free will of the soul, which is involved in all choices having to do with good and evil.