Be able to defend your arguments in a rational way. Otherwise, all you have is an opinion.

Be able to analyze statistics, which can be used to support or undercut almost any argument.

Be able to recognize when you're reading or hearing material biased to your own side.

Be able to confide your innermost secrets to your mother and your innermost fears to your father.

Be able to sneeze without sounding ridiculous. That means neither stifling yourself or spraying your immediate vicinity.

Be able to tell whether garments that look good on the hanger actually look good on you.