Good and evil are both very abstract concepts. Most philosophies accept the dualism of good and evil. Good coexists with evil and there can be no thing such as ‘good’ unless there is ‘evil’ and vice versa.

From a society’s point of view, whatever is beneficial to general mankind is considered good and whatever is not in the interests of the general mankind is considered evil. Therefore, labeling any action as good or evil is clearly based upon one’s perception and judgment. Society has made laws based on precedents of what it has viewed as good and evil. However, these perceptions keep changing with different generations. For instance, it was once considered sacrilege by most societies and religions to abort a fetus. Yet, now with developments in ultrasound technology that can immediately detect any abnormality in the growth of the fetus, more and more couples are deciding to abort a fetus that is not viable as it spares both the child and the parents a lot of pain and misery.

Again, the absence of light cannot be called darkness. Just because the human eye cannot penetrate through the darkness, it does not mean it is ‘dark’. What can be concluded is that the difference between good and evil is not absolute but is relative and of degree.

Good and evil also depend upon the context and results. While an action or a person may be considered good in a certain situation, the same action or person may be labeled bad in another situation. For instance, fire produces warmth during winter. When it destroys property or life, it turns evil.

Also, something that is good for one person may turn out to be evil for another. When a soldier fights for his country, he might kill several people during the war during confrontation. While the soldier will be hailed as a hero in his country, the spouses and children of the people he has killed will view him as a murderer.

Perception of what is good or evil can also be influenced by religions and culture. Some religions accept polygamy whereas other religions consider it as a sin.

Summary:
1. Good and evil are judgment based. When a person finds pleasure out of something, he calls it good. On the other hand, if it brings him misery, he calls it evil.
2. Based on precedents and what is beneficial or detrimental for general mankind, society has made a few laws that bracket certain actions across the world as good and evil. However, just like religious beliefs, this can keep changing with time
3. Labeling an action as good or evil is influenced by the situation, the result, religions and cultures.

Source: https://web.facebook.com/forum9ja/posts/1562620943799700