Jonathan Uesato

“We are talking about a cloak that really and truly renders the wearer completely invisible, and endures eternally, giving constant and impenetrable concealment, no matter what spells are cast at it. How many cloaks have you ever seen like that, Miss Granger?”
Hermione opened her mouth to answer, then closed it again, looking more confused than ever. She, Harry, and Ron glanced at one another, and Harry knew that they were all thinking the same thing. It so happened that a cloak exactly like the one Xenophilius had just described was in the room with them at that very moment.
“Exactly,” said Xenophilius, as if he had defeated them all in reasoned argument. “None of you have ever seen such a thing. The possessor would be immeasurably rich, would he not?”
He glanced out of the window again. The sky was now tinged with the faintest trace of pink.
“All right,” said Hermione, disconcerted. “Say the Cloak existed…what about the stone, Mr. Lovegood? The thing you call the Resurrection Stone?”
“What of it?”
“Well, how can that be real?”
“Prove that it is not,” said Xenophilius.
Hermoine looked outraged.
“But that’s--I’m sorry, but that’s completely ridiculous! How can I possibly prove it doesn’t exist? Do you expect me to get hold of--of all the pebbles in the world and test them? I mean, you could claim that anything’s real if the only basis for believing in it is that nobody’s proved it doesn’t exist!”
“Yes, you could,” said Xenophilius. “I am glad to see that you are opening your mind a little.”
“So the Elder Wand,” said Harry quickly, before Hermione could retort, “you think that exists too?”
― J.K. Rowling, Harry Potter and the Deathly Hallows