Division of Labor
The Industrial Revolution was in its infancy when Adam Smith toured Europe as a tutor. He observed that by separating production into smaller tasks, each handled by a specialized worker, great efficiencies could be had. This division of labor—even without the aid of machinery—is what makes it possible to accumulate capital with which to further production.
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. What is prudence in the conduct of every private family, can scarce be folly in that of a great kingdom.
Today these efficiencies are as important as ever, with division of labor having progressed into supply chains stretching around the globe and advances in communication technology allowing labor to be divided in ways Smith could never have dreamed of.