As far as I know, all references in all "holy" books report that a deity has contacted only one individual at a time. There are no reports of witnesses to any of the reported contacts. This, I think, is a severe under accomplishment for a deity that is alleged to have created a universe.

Medical science has discovered the rate of occurrence of schizophrenia in the human population. Humans have not changed much during the last 10,000 years. It can therefore be assumed that our predecessors suffered from schizophrenia in roughly the same proportions as occurs today.

Schizophrenia is a mental illness that frequently causes people to hear "voices". It has been proved that these "voices" are internally generated by a brain malfunction. One can therefore presume that those who heard "voices" or just one "voice" in ancient times would have ascribed the "voice" or "voices" to a mystical source or a god.

In none of the reported instances is there any reference to new knowledge being imparted to the hearer of the "voice" or "voices". This is consistent with the situation of a sufferer from schizophrenia. The "voice" or "voices" cannot convey any information that the sufferer has not learned previously.

Other hallucinations that include "voices" can be caused by fasting, (a popular religious pastime) bad food, and plants and fungi.

Somebody might know of an instance or two when an alleged deity contacted more than one person at a time. I have not heard of any such instances.

If all references to single individuals hearing the "voice" of god are deleted from "holy" books,
How much would be left?