I like the way that Battler implied that Beatrice was just like
Shrodinger's cat. She can only exist if people believe in her. Thru out episode 1 we have been assaulted with events that "have to be done by a witch", seals that appear after events that had to be done by the witch and gold that came from the witch to make us believe in Beatrice's existence.
The events do not have to be caused by Beatrice. It's only the "belief" that Beatrice caused the events that solidifes her existence.
There's no mystery in saying that it's done by a witch. No fun for me. So I choose to believe in a human cause.