Property, efficiency, the commons, and theft

Economists tell two stories that suggest that property and intellectual property are necessary and sufficient for efficiency. But these two stories, the Tragedy of the Commons and the Parable of Theft, do not actually support that conclusion. The Tragedy of the Commons does not establish the necessity of property because the story applies only if later entrants reduce the enjoyment of earlier entrants. This effect, which I call spreading, is not a universal attribute of all resources, however. The Parable of Theft has a different defect. It must assume that people do not always strike mutually beneficial deals, otherwise society would buy out all thieves and there would be no need for property law to protect producers from them. But if people do not always strike mutually beneficial deals, then giving property rights to producers will prevent their output from flowing, via trade, to those who value it the most.