According to the Merriam Webster Online Dictionary, Common sense is sound, practical judgment concerning everyday matters, or a basic ability to perceive, understand, and judge in a manner that is shared by (i.e. common to) nearly all people.
The thing is that Common Sense is developed over one's lifetime; from learning ( off family, schools, peers), from testing the boundaries, from experimenting, from the culture and communities you operate within and from each and every individual life experience you have had up until the point in time you made your decision.
Even the definition itself says that not everybody shares it; *nearly all people*. So how do we determine if the people we are working with fall within 'nearly all people', or are they the ones whose life experiences have fallen outside of the definition? There's no test to determine what is or isn't common sense, and there's no simple way of determining whether an employee should have common sense in a particular area or not.....
So what are exasperated managers and HR professionals to do, when an employee makes an apparent chuckleheaded decision or error?
Ditch referring to common sense. Remove it from your leadership vocabulary and from your company vernacular. When developing policies, pretend that it doesn't exist. Write your policies to take into account the lowest common denominator.
Presume that your staff are actual human beings, and have diverse and rich and important life experiences which may (or importantly, may not) have given them the knowledge that you assume everyone should have. Treat your employees like humans first, rather than homogenous robots that should take in and retain have the exact same information in the exact same way.
It'll pay off! Promise.