The following are from the Tea Party (Higurashi players, you would know this as the similar thing to the "otsukaresama-kai")
Spoiler for HIGHLY SUGGEST NOT TO READ UNTIL FINISHED WITH TEA PARTY:
Spoiler for The point of Umineko:
Beatriche the Witch does exist. She causes unexplained murders. Batora on the other hand refuses to believe in her existence and steadfastly states that there is no such thing as the supernatural -that the murders can be explained as a trick that can be done by any human. Its human vs the supernatural.
If everyone believes in Beatriche, she will resurrect everyone and take them to the promised golden land. But no miracles occur so long as one person - namely, Batora, refuses to believe in her (the point made in Higurashi)
Batora's take on true miracles: "If the miracles happen because everyone believes in it, that's not a true miracle. A true miracles occurs whether or not one person believes in it or not."
There is one way to defeat Beatriche the Witch. It is to prove that her "magic" can all be explained by tricks compunded to the limits of the physical human world. The world has changed quite a lot in the past 100 years of technological advancement. Can Batora explain the mystery of each of the unexplained murders to "kill off" Beatriche?