To introduce the sovereignty principle, Ripstein invoked a hypothetical example of harmless wrongdoing, one which he assumed that (despite the lack of resulting harm) his audience would agree should be prohibited by the criminal law. In particular, Ripstein argued that the sovereignty principle can do something the harm principle does not: it can explain why harm matters in the cases where it does and also why harm does not matter in the cases where it seems not to do so, as in harm inflicted on oneself, or harm incurred from participating in consensual activities, as a fair contest, for example. He further articulated his own alternative to the harm principle, the 'sovereignty principle,' which attempts to take more seriously the idea that each individual can have a sphere of equal freedom. Ripstein then introduced what was to be the main thesis of his presentation: if we take this idea of sovereignty seriously, it forces us to abandon the harm principle. Ripstein noted that immediately following the passage in which he introduces the harm principle, Mill states that the harm principle serves to create a sphere in which the individual can be thought of as sovereign. Simply stated, the harm principle holds that only those acts that harm or threaten harm to others should be prohibited.

Mill's well-known harm principle, often taken to an important basis for liberal views of the criminal law. Professor Ripstein began his lecture with a reiteration of J.S. Speaker: Arthur Ripstein, Professor of Law and Philosophy, University of Toronto

Mill harm principle summary