hen Thomas Paine appealed to “common sense” to make the case for American independence, it probably never crossed his mind that there would ever be a need to make the case for common sense itself, at least not in America. But common-sense thinking has fallen out of favor. Because it has been under attack for a very long time, it no longer gets the respect it once commanded. Deep thinkers have discarded it, elites have learned to disdain it, and many of us have had our confidence in its value badly shaken. The consequences are enormous. Faltering belief in common...