The tragey of the commons is a type of social trap, often economic, that involves a conflict over finite resources between individual interests and the common good. It states that free access and unrestricted demand for a finite resource ultimately structurally dooms the resource through over-exploitation. The term derives originally from a comparison noticed by William Forster Lloyd with medieval village land holding in his 1833 book on population. It was then popularized and extended by Garrett Hardin in his 1968 Science essay "The Tragedy of the Commons." However, the theory itself is as old as Thucydides and Aristotle.