Private property (n.) is created when a person mixes his labor with the raw materials of nature -(I.E when he makes a piece of land into farmland).
Private property (n.) is forced on us by the human condition, which needs labour and materials to work on; subduing the earth and having dominion are joined.
Private property (n.) is the linchpin of the social contract because it is precisely the protection of one's own property which men seek when they decide to abandon the state of nature.
Private property (n.) is justified in that it is mixing one's labor with external natural materials, thus internalizing them and affording those materials the same rights as one's body itself.
Private property (n.) is, along with well-being, the seat of the justification of the government's authorty. When such protection is no longer present, the social compact can be dissolved.