Philosopher Ian Shapiro says that labor markets affirm self-ownership because if self-ownership were not recognized, then people would not be allowed to sell the use of their productive capacities to others. He says that the individual sells the use of his productive capacity for a limited time and conditions but continues to own what he earns from selling the use of that capacity and the capacity itself, thereby retaining sovereignty over himself while contributing to economic efficiency. A common view within classical liberalism is that sovereign-minded individuals usually assert a right of private property external to the body, reasoning that if a person owns themselves, they own their actions, including those that create or improve resources, therefore they own their own labour and the fruits thereof.