Self-regarding behavior is comprised of actions that concern only oneself, or others who have consented, and do not harm another; this includes behavior which entails a certain degree of possible harm to others, but usually very little. These kinds of behaviors are in what Mill called the private sphere, and society may attach no legal and/or social sanctions of any kind to such behavior. An example of such behavior would be any sort of sexual activity between any number of consenting adults in any combination of gender.
Other-regarding behavior is comprised of actions which cause definite harm to another, or pose such a great degree of risk that harm is nearly certain to occur. These behaviors are in what Mill called the public sphere, and society may, and has the obligation to, attach legal and/or social sanctions to such behavior. An example of such behavior would be sexual activity with a child.
Thus we have the Harm Principle: legal and/or social sanctions are only permissible when one is harmed by another�s actions. Mere notions of morality on the part of society generally is not enough for sanctions to be imposed -- society has the duty to show that real harm comes to someone as the direct result of another�s actions.
Mill also argues that society cannot restrain an individual�s actions to promote that individual�s own good. Part of the reason for this is set forth in the following argument:
1. Since restraint is an evil, the burden of proof is on those who propose such restraint.
2. Since the conduct in question is purely self-regarding, the usual appeal to the protection of the interests of others is not available.
3. Therefore we must consider whether reasons involving reference to the individual�s own good, happiness, welfare or interests are sufficient to overcome the burden of justification.
4. We either cannot advance the interests of the individual by compulsion, or the attempt to do so involves evils which outweigh the good to be done.
CONCLUSION: Therefore the promotion of the individual�s own interests does not provide a sufficient warrant for the use of compulsion.
Therefore society can impose legal and/or social sanctions for engaging in certain behavior only if such behavior causes harm to others. The feelings that other members of society may have are irrelevant.