The confusion of observation and inference is apparent also in the idea that the claimed universality of certain bizarre behaviour is relevant to discussion of the validity of concepts such as mental illness or schizophrenia. The claim is usually made, not that particular behaviour, but that schizophrenia or mental illness, has been found in many cultures. There are a number of examples of this argument, which has been used to defend the activities of classification and diagnosis in psychiatry and, therefore, the inferring of concepts like schizophrenia. A number of attempts have been made to defend psychiatric classification and diagnosis in general, and ‘schizophrenia’ in particular, by drawing comparisons between these and supposedly acceptable aspects of scientific constructs and medical diagnosis. The major comparison of ‘schizophrenia’ with scientific constructs has, of course, been made in attempts to develop an operational definition of schizophrenia.