Both [P. T.] Barnum and H. L. Mencken are said to have....

“ Both [P. T.] Barnum and H. L. Mencken are said to have made the depressing observation that no one ever lost money by underestimating the intelligence of the American public. The remark has worldwide application. But the lack is not in intelligence, which is in plentiful supply; rather, the scarce commodity is systematic training in critical thinking. ”

Carl Sagan

From : Broca's Brain: Reflections on the Romance of Science