ELI5: Explain Like I'm 5

Psychological egoism

Psychological Egoism is a kind of theory about how people act. It says that when people do something, they are always doing it to make themselves feel good. Even if it looks like they are doing something to help someone else, they are really just trying to make themselves feel good. So, mental egoism says that people don't really care about other people's needs and wants, just their own.