Aristotle On Private Property
Paul Meany writes at FEE of Aristotle's arguments on the justification of private property -- noting the "superiority of private property in four core areas: efficiency, unity, justice, and virtue." Here's an excerpt from his piece with the first three:

Efficiency
First, Aristotle argued that private ownership is simply more efficient than communal ownership. The latter increases the likelihood of neglect; since people are sharing something, everyone is more likely to assume that someone else is taking care of the situation, instead of taking responsibility themselves.

As the economist Milton Friedman argued, you spend no money more carefully than your own, and spend no money more liberally than someone else's. Aristotle shared this stance, writing that "people pay most attention to what is their own; they care less for what is common." He asserted that people have an incentive to be productive with what they are uniquely responsible for since they will, therefore, benefit directly from their own efforts. On the other hand, communally owned property will not produce the same incentives because the fruits of people's efforts will not solely be their own. Modern defenders of property tend to stop here, but Aristotle went beyond issues of allocative efficiency, adopting a broader approach.

Unity

Critics of private property tend to demean property as atomistic, claiming that its adoption creates a society of "rugged individualists" who refuse to cooperate with one another. Aristotle sharply disagreed with this view, arguing instead that private property in fact fostered unity, while communally owned property bred constant strife and discord. On the subject of communal ownership, he writes that "in general, living together and sharing in common in all human matters is difficult, and most of all these sorts of things."

Association is not a bad thing by any means, but having people share essential resources in common opens the door to potential conflict and widespread discord; "It is a fact of common observation that those who own common property, and share in its management, are far more at variance with one another than those who have property separately." In owning things for ourselves we avoid the constant strife that arises from compromise with others over the crucial aspects of our lives. Aristotle concludes that "when everyone has his own separate sphere of interest, there will not be the same ground for quarrels."

Justice

In his Nicomachean Ethics, Aristotle asserts that justice is defined by equals getting equal rewards and unequals getting unequal rewards. When this view is applied to the notion of communally owned property, an issue arises. "For if people are not equal, they will not possess equal things, but from this comes fights and accusations... For everyone agrees that the just in distributions must be according to some worth; the worth however, everyone does not call the same thing." For Aristotle, justice constitutes being rewarded what you are worth, therefore unequal abilities result in unequal rewards. Aristotle considers this to be a benefit of the private property system in which people are rewarded whatever price they themselves can command. He believes that in a system of communal ownership, problems are bound to arise where some people work more than others yet receive the same reward. This issue naturally causes discontent, but it is also unjust as it treats everyone equally to the detriment of those who dedicate more of their efforts to working.