Since this question was addressed to me, I'll go ahead and reply, even though the conversation has moved on to cat photos quality.
Of course you can prove the paranormal is true with a simple test, even though you can't prove it's false as easily. If one douser can succeed, or one psychic gets the answers right (without luck or cheating), that proves that dousing or talking with the dead is true. It's not necessary for
everyone to be able to do it.
There's no similar simple test to prove that dousing or talking with the dead is impossible.
Consider it in another field. A few decades ago, there was no way to prove running a 4-minute mile was
impossible, despite the fact no one had ever done it. All it took to prove it was
possible, though, was for one man to do it.