By my estimates, about four percent of the population is evil - that is about one person in twenty five.
The mental abilities of evil people closely echo those of the normal population; there is a bell shaped curve of intelligence in both good and evil people.
Most good people are only aware of the least intelligent part of the evil distribution; those are the people who are obviously evil: criminals. The normal and intelligent ends of the evil distribution totally escape most good people's understanding. In this web page I will describe those undetected parts of evil.
What does an evil person of normal intelligence look like? Most people are very familiar with them. An evil person of normal intelligence is a person who makes life difficult, painful, and unpleasant for the good people around them. The supervisor who creates a crises at work by trying to pour a cup and a half of coffee into a cup and then requires everyone to work holiday's and weekends to clean up the mess - is an example of an evil person of normal intelligence. What distinguishes such people from criminals is that they are quicker learners; they figure out what will happen to them if they pursue the sort of obvious evil things that the least intelligent of the evil spectrum do.
Evil people of normal intelligence are careful to do their best to blend into good society. This insulates and protects them from the angered reaction of good people; who would hammer them just as hard as they hammer the least intelligent of the evil. Indeed, evil people of normal intelligence are so successful at blending into good society that their statements, goals and culture have become 'normal' and 'accepted'. For example, the comic strip 'Miss Peach' is an example of the behavior and actions of evil people of normal intelligence. The 'Put Down', passive aggressive behavior, insults, 'back stabbing', these are all typical behaviors for evil people of normal intelligence. All of these things are so common that many good people adopt them as reasonable ways to behave; they are not, they are as evil as anything could be.
By far evil people of normal intelligence are the most common type of evil person most people encounter. The stress in most good people's lives comes from interaction with evil people of normal intelligence. The goal of the average evil person is to make the lives of those around them as miserable as they can - without doing enough to attract the retribution they richly deserve.
Next up the ladder is the evil person of above average intelligence. These people have a similar goal to evil people of average intelligence; the production of human misery. However these people see the opportunity to do something that evil people of normal intelligence don't see how to do; murder someone and get away with it. They understand that the way to murder someone and get away with it is to not care who they kill, how they kill them, or when they kill them. Such people set up conditions where someone will be 'accidentally' killed and wait for the circumstances to occur.
For example, I once worked for an evil person of above average intelligence who built up a company which did about twenty million dollars a year of business. He was only interested in his business as an instrument to his ends. He worked people long hours of overtime (without any extra pay) - he pushed people as hard as he could. What he was doing was setting up an environment as stressful as he could - secure in the knowledge that sooner or later - a death would be the result. Sure enough, a staff accountant driving home after a late night's work was hit by a drunken driver and killed. The boss was stunned; his life's goal had been accomplished - the guilt was obvious in his face the next day. He became very cheerful over the next several weeks, and lost interest in the company. Inside of a year and a half it was out of business.
Of course since he was cloaked in plausible deniability no criminal charges could ever be brought against him. But, he could see that the death had come as a direct result of his deliberately malicious behavior; he willed it, and it happened. Most industrial accidental deaths and injuries can be traced back to the malicious behavior of those who are evil and of above average intelligence.
That leaves us those who are evil and of high intelligence. Most good people are also familiar with these kind of people; we call them leaders - both of industry and of government. It is the goal of such people to get away with mass murder. An example will show how they work their agenda.
If you look at the Viet Nam War none of it makes much sense; not from a political standpoint, not from an economic standpoint, and certainly not from a military standpoint. Let us examine the well known case of 'Hamburger Hill'; a battle location in the Viet Nam war. In this engagement US forces fought their way up a hill against fierce opposition. Once the US forces had taken the hill they were ordered to MARCH BACK DOWN giving the hill back to the opposition. The action was repeated several times. The argument given was that the US forces were exhausting the enemy by forcing them to fight repeatedly. Of course the conventional military strategy is to exhaust the opposition forces by making them attempt to re-take the hill by force of arms - rather than by giving it back to them uncontested. The 'Hamburger Hill' strategy makes no sense whatsoever - unless you assume that very high up in the US government was an evil person of high intelligence whose goal was to murder ten's of thousands of people and get away with it. When thought of this way, the entire War in Viet Nam snaps into focus and makes sense - as far as I know, that is the ONLY explanation of the war that allows it to be understandable.
If you are a good person you will meet many evil people in your life, you need to recognize them and their actions. More importantly you need to recognize which evil behaviors you have been conned into excepting as reasonable and to reject those behaviors - both in yourself and in others - as unacceptable.
Of course Yin and Yang complicates the detection of evil; in any good person there is an element of evil - in any evil person there is an element of good. In a good man that element of evil belongs in his fighting spirit - where it causes no harm and strengthens his nature. Incidentally, it is because of this element of evil in the fighting spirit that good triumphs over evil; it is something evil lacks.