I’ve just finished the John Stuart Mill classic On Liberty. JSM was a 19th century philosopher and political economist. Inter alia, JSM is famous for his refinement of the harm principle. The harm principle is a foundation of modern libertarian (or classical liberal) thought. The HP as explained by JSM-
The only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others. His own good, either physical or moral, is not sufficient warrant… The only part of the conduct of anyone, for which he is amenable to society, is that which concerns others. In the part which merely concerns himself, his independence is, of right, absolute. Over himself, over his own body and mind, the individual is sovereign.
Well, what about drug abuse? People do bad things on drugs. Shouldn’t we just ban drugs so people won’t harm others while high? JSM offers a radically simple solution. Instead of banning substances, we should only hold men responsible for actions that harm others. JSM explains-