The Wealth of Nations by Part 4 Chapter 3 Page 67

They even profit by his underselling the poorer workmen who deal in the same way with him. The manufacturers of a rich nation, in the same manner, may no doubt be very dangerous rivals to those of their neighbours. This very competition, however, is advantageous to the great body of the people, who profit greatly besides by the good market which the great expense of such a nation affords them in every other way. Private people who want to make a fortune never think of retiring to the remote and poor provinces of the country, but resort either to the capital, or to some of the great commercial towns. They know that where little wealth circulates there is little to be got, but that where a great deal is in motion, some share of it may fall to them.

The same maxims which would in this manner direct the common sense of one,