[Without trade restrictions] "the obvious and simple system of natural liberty establishes itself of its own accord. Every man... is left perfectly free to pursue his own interests in his own way... The sovereign is completely discharged from a duty [for which] no human wisdom or knowledge could ever be sufficient; the duty of superintending the industry of private people, and of directing it towards the employments most suitable to the interest of the society", The Wealth of Nations, Book IV Ch.IX