The Experience of Hallucinations in Religious Practice
by Robert Pearson
"The Experience of Hallucinations in Religious Practice" by R.S. Pearson is the one of the first books to help distinguish what is a spiritual experience and what may be merely a type of dream phenomena or hallucination. This book discusses psychological ideas that show the longer that you hallucinate, the more your IQ can decrease, and tries to point towards authentic spiritual experience.