Etymology

Noun

1. An internal sense, formerly believed to be the sense by which information from the other five senses is understood and interpreted.
   • 1621, Robert Burton, The Anatomy of Melancholy, Book I, New York 2001, p. 159:

     This common sense is the judge or moderator of the rest, by whom we discern all differences of objects; for by mine eye I do not know that I see, or by mine ear that I hear, but by my common sense [...].

2. Ordinary sensible understanding; one's basic intelligence which allows for plain understanding and without which good decisions or judgments cannot be made.

   To act with common sense, according to the moment, is the best wisdom I know; and the best philosophy, to do one's duties, take the world as it comes, submit respectfully to one's lot, bless the goodness that has given us so much happiness with it, whatever it is, and despise affectation. - Horace Walpole