true enough. good or bad is based on the norm of the society. go with norm= good. against norm= bad.

that's why people from different society don't always agree with each other on some values.

about the ying yang thing and juggle between good and evil it all depends on how the society works.

how about utilitarian principle where some must be harmed for the good of the majority?

let's have a virtual moral test
here's the train moral dilemma:

1)Put yourself in this situation.

You are at a train track and see five people tied to the track ahead. A switch is in front of you which will divert the train, but as you look down you see a man is strapped to that track and will be killed. Is it permissible to flip the switch and save the five people at the expense of one?

2)Now imagine in order to save the five people, you have to push a stranger in front of the train to stop it. You know for certain it would stop the train in time to save the five people tied to the tracks. Is it permissible to push the man and save the five people at the expense of one?