What can be property?

The two major justifications given for original property, or homesteading, are effort and scarcity. John Locke emphasized effort, "mixing your labor" with an object, or clearing and cultivating virgin land. Benjamin Tucker preferred to look at the telos of property, i.e. What is the purpose of property? His answer: to solve the scarcity problem. Only when items are relatively scarce with respect to people's desires do they become property. For example, hunter-gatherers did not consider land to be property, since there was no shortage of land. Agrarian societies later made arable land property, as it was scarce. For something to be economically scarce, it must necessarily have the exclusivity property - that use by one person excludes others from using it. These two justifications lead to different conclusions on what can be property. Intellectual property - non-corporeal things like ideas, plans, orderings and arrangements (musical compositions, novels, computer programs) - are generally considered valid property to those who support an effort justification, but invalid to those who support a scarcity justification, since they don't have the exclusivity property (however they may still support other 'intellectual property'-laws such as Copyright, as long as these are a subject of contract instead of government arbitration). Thus even ardent propertarians may disagree about IP. By either standard, one's body is one's property.

From some anarchist points of view, the validity of property depends on whether the "property right" requires enforcement by the state. Different forms of "property" require different amounts of enforcement: intellectual property requires a great deal of state intervention to enforce, ownership of distant physical property requires quite a lot, ownership of carried objects requires very little, while ownership of one's own body requires absolutely no state intervention.

Many things have existed that did not have an owner, sometimes called the commons. The term "commons," however, is also often used to mean something quite different: "general collective ownership" - i.e. common ownership. Also, the same term is sometimes used by statists to mean government-owned property that the general public is allowed to access (public property). Law in all societies has tended to develop towards reducing the number of things not having clear owners. Supporters of property rights argue that this enables better protection of scarce resources, due to the tragedy of the commons, while critics argue that it leads to the 'exploitation' of those resources for personal gain and that it hinders taking advantage of potential network effects. These arguments have differing validity for different types of "property"—things that are not scarce are, for instance, not subject to the tragedy of the commons. Some apparent critics advocate general collective ownership rather than ownerlessness.