Psychosis is often characterized as 'loss of contact with reality.' Three

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Psychosis is often characterized as 'loss of contact with reality.' Three questions. (1) What is this 'reality' of which they speak? (2) Does anybody (even psychatrists) really know enough about this 'reality' to be able competently to deliver a diagnosis under that characterization? (3) What is this 'contact' of which they speak