linguistic:paraphrasing
Principle

The two major justifications are given for the original property, or the homestead principle, 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 concerning 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 —incorporeal 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 the things don't have the exclusivity property (however, those who support a scarcity justification 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. In contrast, requesting one's own body requires absolutely no state intervention. So some anarchists don't believe in property at all.

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 entirely 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 reduce 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. At the same time, critics say 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.

Things that do not have owners include: ideas (except for intellectual property), seawater (which is, however, protected by anti-pollution laws), parts of the seafloor (see the United Nations Convention on the Law of the Sea for restrictions), gases in Earth's atmosphere, animals in the wild (although in most nations, animals are tied to the land. In the United States and Canada, wildlife is generally defined in statute as property of the State. This public ownership of wildlife is referred to as the North American Model of Wildlife Conservation and is based on The Public Trust Doctrine.), celestial bodies and outer space, and land in Antarctica.

The nature of children under the age of majority is another contested issue here. In ancient societies, children were generally considered the property of their parents. However, children in most modern communities theoretically own their bodies but are not regarded as competent to exercise their rights. Their parents or guardians are given most of the fundamental rights of control over them.

Questions regarding the nature of ownership of the body also come up in the issue of abortion, drugs, and euthanasia.

In many ancient legal systems (e.g., early Roman law), religious sites (e.g. temples) were considered property of the God or gods they were devoted to. However, religious pluralism makes it more convenient to have sacred sites owned by the spiritual body that runs them.

Intellectual property and air (airspace, no-fly zone, pollution laws, which can include tradable emissions rights) can be property in some senses of the word.

Ownership of land can be held separately from the ownership of rights over that land, including sporting rights, mineral rights, development rights, air rights, and such other rights as may be worth segregating from simple land ownership.