Mill's Harm Principle

Does Mill ever state why harm is bad?
If not, why is harm bad? Is it simply a moral decision? Do we implement legal moralism in our legal codes to prevent harm?

Moved to HoQ.

If harm isn’t bad, what is?

Maybe nothing is intrinsically bad. Maybe everything we perceive as “bad” is a moral decision.

Mill doesnt explicity define harm but he does make a distincition of self-regarding behavior and other regarding behavior. Once harm starts to interfer with others, the government has a right to regulate it. You should try to contrast the harm principle with Mill’s other principles like legal moralism, perternalism, legal offensive, legal welfare to get a better understanding of what’s not considered harm