How do you define 'evil' within the context of atheism?
I think harm is the most important metric of evil, without gods or dogma that define right from wrong.
When a person capable of understanding what s/he is doing cases harm or injury through malice, irresponsibly, irrationality, or injustice, I would call that evil. The greater the harm, the greater the evil.
Behavior or action that causes harm through intent or willful ignorance with the cognitive ability to know what you are doing is wrong. Belief in a mythical supernatural being or beings does not excuse you from being responsible for your actions nor does it mitigate the harm you cause to others.
When you come to make a moral action (any action which affects other people), then each person whom that action affects is to receive the maximum benefit and minimum harm. Anything else is evil, or bad, or falling short of goodness, whichever term you prefer. I think that to qualify as "evil" then there has to be some intention to do wrong.
Perhaps the word "evil" is a bit inappropriate in a secular setting because it has so many supernatural connotations. Evil forces, the evil one, and such. Doing evil, is going against god and must be avoided at all cost; even at the expense of your own family or any other people.
Plenty of other words such a malicious, malevolent, vengeful, miscreant, violent, misguided, warped are grounded in human relations.
Personally, I like the Taoist philosophy: there is no good and evil, only different points of view.
Rapists rape for a reason... lust, psychosis, whatever else.... they are not inherently evil.
Murder provides a better picture... some people say spiders are evil but really, spiders just want to live their life on their own, building webs and eating flys.
Just to clarify, I'm not saying rape and murder are good, or even tolerable. Just that evil isn't the right word for it. To me, evil is an objective statement and I don't think we can apply the term accurately given that we don't know an objective definition of evil.
So, rapists rape for a reason. So what, don't carnivores murder for a reason? Isn't elective, recreational rape worse than the non-choice of eating to survive?
Also, why are we comparing human sexual assault behavior to that of non-thinking carnivorous species? Rapists are not to rape as spiders are to eating to survive.
WTF, man. Maybe a better evaluation would be to look at the morality of elective meat-eating vs. carnivorous meat-eating.
Yeah it's a bit of a poor example I guess... My point is that evil is objective. Despite the fact that rapists are doing wrong, I don't think we can call them objectively evil given the subjective nature of our own point of view.
In the case of rapists, they are probably mentally ill. They need help, not a label that reads: evil.
It is hard to define "evil" like it is hard to define "no light" or "no heat". Instead it is easier to define heat, and light, and good.
Evil is what is not good.
Actually one of my favorite discussions of this comes from the graphic novel Digger. Here's how the protagonist tries to define evil, and how her wiser friend defines it properly. (Courtesy of the internet archive, since Digger's website seems to be down.)