harm principle It is often suggested, sometimes even by *libertarians, that actions that harm other people should not be allowed. But taken literally, this cannot be correct. For we often *objectively harm others, or *risk harming them, with their permission: such as by providing them with ‘junk food’, cigarettes, or participatory *sports. Harming, or risking harming, others on a voluntary basis is part of *liberty. A better criterion of what should not be allowed is what *proactively imposes on other people (or normal adults, at least; with the mentally impaired, etc., being treated like *children of similar intellect), even if it does the imposed-on people some objective good.

A Dictionary of Libertarianism