A book on the Roman Empire made the following observation: “Romans bought their pots from professional potters, and bought their defence from professional soldiers. From both they got a quality...

A book on the Roman Empire made the following observation: “Romans bought their pots from professional potters, and bought their defence from professional soldiers.

From both they got a quality product—much better than

if they had had to do their soldiering and potting themselves.” Briefly explain what economic concept the author

is illustrating in this passage. How does he know that

Romans got better pots and better defense by relying on

this economic concept?

Source: Bryan Ward-Perkins, The Fall of Rome and the End of Civilization,

Oxford: Oxford University Press, 2005, p. 49.