Smith was both extending and breaking with the analysis of the Physiocrats, political economists of eighteenth-century France who believed that the natural productivity of the land, set in motion by agriculture, was the origin of all wealth. For them, surplus value--the "additional" value produced between input and output in a production process--was possible only as a gift from nature. Their policy conclusion was logical if agriculture was the source of the surplus upon which the state and all society depended, then anything that hindered it (taxes, trade restrictions, etc.) was bad.