This guy is the Mental Heath Science equivalent of the current crop of Global Warming deniers.
No, hearing voices is not alway a sign of Schizophrenia, but it is an indication of some sort of internal problem with the brain such as Frontal Lobe Epilepsy or various different types of poisoning.
And no, hearing voices is not the same as the inner dialog that most of us have, that's called thinking and that IS normal. People who actually "hear voices" do not recognize those "voices" as coming from inside their own brain, they think (for reasons we don't fully understand yet) that those voices are external, even though they are just internal thoughts that have been mis-routed in some way, inside their own brain.
I have several people in my family (as does this author) who have had, or are still having, auditory hallucination, but the difference is, my family is not in active denial of the problem, as this author is.
Also, I've lost two of my best friends in the last 6 years to suicide and both of them had obvious (to me) Mental Illness, yet both of them (and their families) thought they could overcome their problems without treating their Mental Illness, by turning to religion. Both of them failed and both are now dead. One at age 43 and the other 35, but believe me, being right about the fact that your friend needed treatment for Mental Illness after they have killed themselves is no comfort at all.
It's very sad to me that books like this, written by these so-called "experts," get equal or even greater respect from most people than do the current scientific research into this area, an area that the scientific community are finally making major progress in, thanks to new technology's like the CAT Scans and PET Scans.
But hey, as Stephen Colbert likes to joke, it's the
"Occam's razor" school of thought that so many anti-scientific folks love to use these days to justify their inability to just say the words, "I don't know" or "I don't understand." And what is behind that inability? Pride (one of the seven deadly sins).
About Occam's razor
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http://skepdic.com/occam.html>
That's all I'm going to say about this and I'm sure I haven't changed your feelings about this, but as The Buddha taught, I can not show you The Path and expect you to understand it, this is a path you must travel yourself to understand.