- Book IV is called "Of Systems of Political Economy."
- For Smith, there are two main goals for the science that he calls "political economy": the first is to provide prosperity for the people of a country, and the second is to create enough funds for public institutions (like schools, roads, and hospitals).
- As far as he can tell, the world has tried two different ways of organizing the economies of countries. The first is called the "system of commerce" and the second is the "system of agriculture." Smith wants to start with explaining the system of commerce.