Previously we defined peaceful human relations as relations from which force is absent. The concepts of property and ownership help us to apply this idea more specifically. In a peaceful society, Crusoe has ultimate control over his life and over his other property as an extension of that life, but he cannot interfere with Friday's life or property without Friday's implicit or explicit consent. Friday, of course, extends the same courtesy to Crusoe. It should not be concluded, however, that Crusoe and Friday necessarily practice rugged self-sufficiency. If their relationship is friendly, Crusoe may offer some of his thatch as a gift to Friday, thereby obtaining psychic utility and maximizing his position on his subjective value scale. Friday may be a frequent and welcome visitor to Crusoe's tree house, and Crusoe may let him borrow the facility while Crusoe goes on vacation to the opposite end of the island.

Even if Crusoe's and Friday's relationship is more distant, they will almost certainly both realize gains in subjective utility through voluntary exchanges of goods and services. A market is a connected set of exchanges of two or more goods among two or more individuals. If the exchanges in a market are not affected by the use of force, we call it a free market. In a broader sense, we may use the phrase free-market society to denote a society based on peaceful human action—i. e., in accordance with the ownership principles just developed.