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 the 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
or maintain.
- Smith, Wealth of Nations (1776)