There is a fairly common riddle
You're standing between the door to heaven and the door to hell. A guard stands by each door. One guard always tells the truth, and the other always lies. You don't know which guard is which. What one question can you ask a guard to find out which door leads to heaven?
I came up with
Are you capable of speaking the statement 'This is the door to heaven'
Does this work?
For reference the standard answer to this riddle is
Which door would the other guard say goes to heaven?