A Problem with Harm Principal
Where, in Chapter I of On Liberty, Mill stated the harm principal as writen above. At the beginning of Chapter IV he suddenly, and inexplicably, includes the word interests. He never explained this change, and whether he was even aware of it is under question. It, of course changes the "very simple theory" into a more unclear, much larger theory. Where, under the first Harm Principal one could act as long as ones actions did not physically harm someone, one now needs consider their emotion. For example:
In ones pure private life one may choose to sunbathe naked clearly visable to those on the street as well as ones neighbours. Under Harm Principal the First, this is perfectly alright - no one is being injured by this action, they can, afterall, overt their eyes. Under the second Harm Principal, the neighbour who happens to be deeply and grievously offended (her mother happens to be over) needs be taken into account.
As can be seen - this is a far more complex, almost incalculable, moderation - interests have the potential to conflict and contrast. One's out of sight activities which were previously perfectly acceptable now come under question, as in example the second:
A homosexual decides to come out, so to speak, to ones family and friends. Sadly, however the homosexuals mother had been planning on meeting a partner of the opposite sex - these are her interests. By informing her of sexuality, the homosexual is contrasting the previous interests of the mother and, according to the Harm Principal II, is harming the mother.