The theory that can absorb the greatest number of facts, and persist in doing so, generation after generation, through all changes of opinion and detail, is the one that must rule all observation.

Later Marxian economics descending from classical economics also use Smith's labour theories in part. In addition he was in favor of retaliatory tariffs and believed that they would eventually bring down the price of goods. According to Boswell he once told Sir Joshua Reynolds that 'he made it a rule when in company never to talk of what he understood'.

Adam Smith (5 June 1723 OS – 17 July 1790) was a Scottish moral philosopher and a pioneer of political economy. In 2009 Smith was named among the "Greatest Scots" of all time in a vote run by Scottish television channel STV. He died in 1790 at the age of 67.