QUOTE: Extraordinary claims require extraordinary evidence was a phrase made popular by Carl Sagan. It is the heart of the scientific method, and a model for critical thinking, rational thought and skepticism everywhere.
The evidence put forth by proponents of such things as gods, ghoasts, the paranormal, and UFO's highly questionable at best and offers little in the way of proof. Even if we accepted what evidence there is as valid (and it is highly debatable if we should), limited and weak evidence is not enough to overcome the extraordinary nature of these claims.