A banker, merchant, or manufacturer is likely to be more intelligent than a tradesman, because he has larger and more complicated interests to manage.
 John Stuart Mill, Considerations on Representative Government (1861). copy citation

Context

“An employer of labor is on the average more intelligent than a laborer; for he must labor with his head, and not solely with his hands. A foreman is generally more intelligent than an ordinary laborer, and a laborer in the skilled trades than in the unskilled. A banker, merchant, or manufacturer is likely to be more intelligent than a tradesman, because he has larger and more complicated interests to manage. In all these cases it is not the having merely undertaken the superior function, but the successful performance of it, that tests the qualifications; for which reason, as well as to prevent persons from engaging nominally in an occupation for the sake of the vote, it would be proper to require that the occupation should have been persevered in for some length of time” source