I commented that without a state there would be no such legally defined thing as private property—since there would be no laws. So the notion of private property depends crucially on the existence of a state and of laws that define what private property means and what legal rights and obligations go along with it.
I went on to look up the issue in the Stanford Encyclopedia of Philosophy. David Hume, as usual, got to the heart of it.
There is nothing natural about private property, wrote Hume. The ‘contrariety’ of our passions and the ‘looseness and easy transition [of material objects] from one person to another’ mean that any situation in which I hold or use a resource is always vulnerable to disruption (Hume 1978 , p. 488). Until possession is stabilized by social rules, there is no secure relation between person and thing. We may think that there ought to be: we may think, for example, that a person has a moral right to something that he has made and that society has an obligation to give legal backing to this moral right. But according to Hume, we have to ask what it is in general for society to set up and enforce rules of this kind, before we can reach any conclusions about the normative significance of the relation between any particular person and any particular thing.
Our property is nothing but those goods, whose constant possession is established by the laws of society; that is, by the laws of justice. Those, therefore, who make use of the words property, or right, or obligation, before they have explained the origin of justice, or even make use of them in that explication, are guilty of a very gross fallacy, and can never reason upon any solid foundation. A man's property is some object related to him. This relation is not natural, but moral, and founded on justice. It is very preposterous, therefore, to imagine, that we can have any idea of property, without fully comprehending the nature of justice, and shewing its origin in the artifice and contrivance of man. The origin of justice explains that of property. The same artifice gives rise to both.