 Libertarianism is committed to a strong guarantee of basic liberty of action. However, even views that endorse the strongest possible form of self-ownership do not guarantee such liberty. For if the rest of the world (natural resources and artifacts) is fully owned by others, one is not permitted to do anything without their consent—since that would involve the use of their property. Since agents must use natural resources (occupy space, breathe air, etc.), free people require rights to use parts of the external world.