Manners are a sensitive awareness of the feelings of others. If you have that awareness, you have good manners, no matter what fork you use. (Emily Post)

But I would add that human beings are not necessarily born with a sensitive awareness of the feelings of others. They have to have parents who set an example for a start, and once an example is being set, they have to be corrected constantly until consideration of others becomes second nature. If they don’t have that start in life they will be likely be selfish boors all they lives.