Spiritually speaking, your opinion on the flying man?

A man claims he can flap his arms and ascend into the air. You ask him to prove it. He fails to prove it. Is it reasonable to assume he can't or would I have to provide evidence he can't? What if I fail to provide evidence that he can't fly, should I come to the conclusion that he can fly considering that no evidence for him having the ability to fly isn't evidence against him having the ability to fly, therefore he can fly?