If you have it and you know you have it, then you have it. If you have it and don't know you have it, you don't have it. If you don't have it but you think you have it, then you have it.
“The head of a ship however has not always an immediate relation to her name, at least in the British navy.”
“I didn't know the city at all, but I was so happy to be in New York I cried. I was so excited.”