… is from pages 128-129 of the 1971 Augustus M. Kelley reprint of the 1880 Sixth American edition  of Jean-Baptiste Say ’s 1803 A Treatise on Political Economy  (Traité d’économie politique):
There are some truths so completely self-evident, that demonstration is quite superfluous. This is one of that number. For who will attempt to deny, that the certainty of enjoying the fruits of one’s land, capital, and labour, is the most powerful inducement to render them productive? Or who is dull enough to doubt, that no one knows so well as the proprietor how to make the best use of his property?
DBx: Sadly, the world today is filled with people who are indeed so dull – so dull despite, in many cases, boasting terminal degrees in subjects such as economics, philosophy, and law from universities sporting names such as M.I.T., Columbia, and Harvard.