I think common sense is real. Knowing the difference between right and wrong...weighing the consequences of one's actions and selecting the option that serves in your best interest or that of another. The choices one makes in life can be different for you and me as long as it is not at the expense of hurting others.

To me, common sense is inherent and partially learned (as Lizardlady said). You teach a child not to touch a hot stove or they will burn themselves (consequence). The child hears you but they are not convinced or don't really understand what you are saying. The child puts their hand on the stove but not near the flame. They think this is not bad, the stove doesn't hurt and so they go further and touch the grate...OUCH! That hurts! (learned)

Even the law recognizes common sense. The plead for insanity is based on the lack of having common sense (seeing the consequences of your actions). The claim is that they were so overwhelmed with emotion/fear/love/jealousy that all common sense was lost in the heat of the moment and insanity prevailed.

Not sure where I'm going with my thoughts here but maybe common sense vs. insanity.