Diagnostic of schizophrenia, they arise when an ordinary event assumes a special significance for the sufferer.
One schizophrenic overheard two people talking about a friend in a shop and assumed they were talking about a blasphemy he had committed him which rendered him an outcast and a heretic. Another man, on being handed a biscuit by his brother-in-law, suddenly 'realised' that his brother-in-law was accusing him of being a homosexual and was organizing a gang to spy on him.