Do I have Common Sense?

What is Common Sense? Does it actually exist, within all of us?

Web Definitions
Common = Prevalent
Sense = Keen intuitive awareness of or sensitivity to the presence or importance of something;
Common Sense = Good sense and sound judgment in practical matters

Thing is, the actual definition of this concept is anything BUT common, isn't it?
Sense and judgement is never based on only one variable.
In reality, a true dichotomy is close to impossible.
As such, a decision is surely based on many different factors,
some of which we consciously consider, some of which we unconsciously do so, some of which we don't consider at all.
How exactly do we determine a person's "good sense and sound judgement"?

Is it then, in"common sense”ical" to judge?