Free trade raises our standard of living, not by adding jobs, but by increasing what Adam Smith called the division and specialization of labor, making jobs more productive.
When individuals in other nations suffer the economic pain of inflation through declining investment, we too hurt for the natural expansion of the global division of labor that authors our economic specialization being halted to varying degrees.
They help the reader understand that the division of tasks leads to the greatest amount of specialization, and with specialization comes the greatest amount of production.