For all you Christians out there can I ask you a quick question?

For those of you who are both Christians and psychologists why then do some of you believe that a burning bush talked to Moses and not that he had a auditory hallucinations? Why do some believe that the sky talked to Abraham? Could it all just be mental illness? I mean read the bible. Clearly it is ranting of deranged lunatic and trust me if you guys heard a similar story you guys would too assume that the person was downright crazy.