Adam Smith extended the theory of natural liberty to the realm of economics, formulating the classic statement in favor of free trade.
It is the maxim of every prudent master of a family, never to attempt to make at home what it will cost him more to make than to buy. The taylor does not attempt to make his own shoes, but buys them of the shoemaker.
The shoemaker does not attempt to make his own clothes, but employs a taylor…. What is prudence in the conduct of every private family, can scarce by folly in that of a great kingdom. If a foreign country can supply us with a commodity cheaper than we ourselves can make it, better buy it of them with some part of the produce of our industry.
According to the system of natural liberty, the sovereign has only three duties to attend to: … first, the duty of protecting the society from the violence and invasion of other independent societies: secondly, the duty of protecting, as far as possible, every member of the society from the injustice and oppression of every other member of it, or the duty of establishing an exact administration of justice; and, thirdly, the duty of erecting and maintaining certain public works and certain public institutions, which it can never be for the interest of any individual, or small number of individuals, to erect and maintain.