What Is the Criterion of a Hallucination?

Jess went to a healing centre in glastonbury, where she met other people with similar experiences. Psychologists and researchers are looking into the community of 'non clinical voice hearers' The type of work going on at centres like this has started to interest not just psychic mediums, but research scientists too. Just that single symptom of hearing voices can be enough to diagnose someone with psychosis.