 Many economists regard the public-goods problem as a justification for advocating coercive government action (e.g., Sidgwick 1901; Pigou 1920 [1932]; Samuelson 1954). The argument actually goes back to the origins of economics. In Book 5 of the Wealth of Nations, Adam Smith listed three functions of government. “The third and last duty of the sovereign or commonwealth,” Smith says,