Property appears an abstract, transcendent, metaphysical concept from afar but on closer inspection reveals itself to be legally constructed. Like ‘person,’ property obtains its philosophical traction from a legal, economic, and social imperative to distribute resources, and thus, wealth and power. As a canonical legal textbook puts it, the “property system” that results from a particular set of legal arrangements can “order relations”; it can “confer benefits and impose burdens.” The law describes how it is acquired by discovery, capture, creation, being found, adverse possession, and gift. These accommodations of property are so fundamental that property is written into our conceptions of ourselves, in claims that “every man has a property in his own person.”
This taxonomy of ways of acquiring property highlight particular modes of interaction with the world in terms of their property creation properties: ‘this way of interacting with the world counts as an acquisition of property if it meets the requisite legal conditions’; the workings of the common law of property are refinements, over an extended period of time, of these interactions. Law thus provides a specification of the conditions under which humans interact with the world to bring property into being, and how other humans should accordingly interact with a world in which property exists, if they are to avoid particular consequences arising from regulations that preserve the categorization of particular objects as property. (Computer software—in its binary and text forms—had to be legally demarcated as ‘ownable’ and ‘copyrightable’ before it could be termed ‘property’ of any kind.) These consequences could, for instance, interfere with ends and purposes served by the provision of private property. The law of property demarcates a range of possible actions and restrictions on our freedom; various pushings, proddings, and pokings of the world become illicit because they may constitute, for instance, ‘trespass on chattels.’ This categorization of the world into property and not-property acquires ontological significance: property becomes part of our socially constructed reality, reconfigurable if social needs change.
Property is not discovered; it is made, not by the act of mixing labor with supposedly ‘fallow land,’ as Locke would have had it, but by the scaffolding provided by the surrounding legal system. Property is a wholly positivistic legal concept; it makes a supposedly natural right ‘real’ and acquires its ontological weight from law. The legal conceptions of property are indifferent to the kinds of property system they create: different sets of rules create different systems, with different balances of power for owners and others; such allocations of property might lock in and preserve existing power relations.
The best justifications—philosophical ones—for system of property are pragmatic, outcome oriented ones. There is no ‘natural’ or ‘objective’ independent basis upon which to rest the ‘protection’ of property:
The property concept had no determinate meaning or positive content. It was a contingent decision whether the owner of the factory machinery should also own the products of the factory, or whether the owner also should control the management of the plant. [Gary Peller, The Metaphysics of American Law, 73 Cal. L. Rev. 1151 (1985)]
Samir Chopra 
So an agreement, designed according to what makes sense. Of course, this “sense” gets rather complicated.
The simple story is that property should be fair, distributed according to one’s desert. However, how to establish desert? If I inherit a million dollars, I certainly did nothing to deserve it, in that I played no part in its creation. But maybe it is fair to respect the wishes of the deceased. But what if they inherited it, and so on?
Let me toss another piece of wood into the fire: as a behaviorist, I can make a rather solid case that all of our actions in life are in a sense “inherited”, in that they are entirely a function of our genes and our environment. As such, any action we take to create wealth is inherited.
This may seem a fanciful stretch, even if you accept the premise that our actions are not our own. Surely we must act as if they are. As a practical matter, maybe this is true. However, we certainly don’t act this way at a societal level. In criminal justice, people are judged to be responsible for their actions, and thus deserving of a range of punitive measures. In our economic system, people are assumed to have “earned” their fortunes – or lack thereof. As such, property is hardly given a second thought as the direct result of personal action.
If our actions are inherited, then all forms of property inequality (not to mention other forms of capital) are injust. As a practical matter, remedying this injustice in a complex society is obviously no easy task. History is riddled with horrific results of experimentations in equality. However, it is also filled with examples of successes (public schools, libraries, parks, social security, medicaid, etc.).
Many of our political arguments are over the practical effects of social responses to equality – whether or not they would work, whether we can afford them, whether they have secondary negative effects and so on. Yet, first we must establish whether or not there is a moral imperative, a problem to address. And at this point, a good-as majority of the country simply disagrees with the premise that we inherit our actions, much less that social interventions might be effective.
A strange irony is that many of these very same people view social interventions as having negative effects on motivation, which is a completely behavioral analysis, and would as such seem to agree with the premise they deny in the first place!