What was John Stuart Mill's (1806-1873) Harm Principle? -How does this influence the Role of the State?

The harm Principle was JS Mill's Theory that Individuals are their Masters in Every Way. No Intervention should occur unless it is harming others -It is thus Acceptable to harm oneself, but no one else. For example, Liberals wouldn't ban Smoking but may ban Smoking in a Pub or restaurant. -But causing too much Harm to oneself can affect others, like Family Members. This should be Prevetned too. -The State should only intervene when its Necessary to Protect Society. Other than that, it should allow Individual Libetty by being Restricted