A child returns home with a writing assignment and asks his father for help. "Dad, can you explain the difference between 'potential' and 'reality'?"
His father thinks for a moment and says, "I'll show you. Go ask your mother if she would sleep with Robert Redford for a million dollars. Then ask your sister the same about Brad Pitt. Come back and tell me what you've learned."
Puzzled, the boy does as he's told. He asks his mother, "Mom, if someone offered you a million dollars, would you sleep with Robert Redford?"
His mother glances around slyly, smiles, and whispers, "Don't tell your father, but yes, I would."
He then goes to his sister's room and asks, "Sis, for a million dollars, would you sleep with Brad Pitt?"
His sister exclaims, "Oh my god! Absolutely!"
The boy returns to his father and reports, "Dad, I think I understand. Potentially, we're sitting on two million bucks. But in reality, we're living with two tramps."