Do you keep kosher?  Let’s say someone sat down next to you on an airplane.  Say, an evangelical Christian.  Or a Messianic Jew.  Or a completely unaffiliated Jew.  And saw you eating your own kosher-packed food.  And asked you:
“Why do you keep kosher?”

Could you answer the question?  Without hesitating?  Without stuttering?
If you pray daily, and were sitting on the plane next to someone, who asked you:
“Hey.  What is that hymnal?” 

What would you respond?  Could you, on the spot, articulate a coherent answer?
What if they just noticed a hamsa, or a chai, or that your name is Bergerstein, and asked:
“May I ask you something I’ve always wondered?  What do Jews believe?”

What would you answer?
What if they said:  Why is there so much fighting in the Land of Israel?  Is it true that different kinds of Jews don’t get along?  Why are you wearing a kippah?  What are those fringes [tzitzis]?
Recently I taught a class in which I challenged the participants to articulate one or two sentences that would express, whether to a child or adult, why it’s important to be and stay Jewish.  What would you say?  Do you know what you believe?  Do you know why you believe it?  Are you proud to be a Jew?
Or, as Dr. Suess might ask:  “What would you do if someone asked you?”