In these series of articles honouring John Marshall for his contributions to psychology, linguistics, the history of ideas and many other fields we should not forget his contribution to psychiatry. This has been mostly from the point of view of a critical observer, but also someone deeply interested in the application of cognitive neuropsychology to a broader range of disorders than the traditional ones. This “cognitive neuropsychiatric approach” is discussed in relation to attempts to understand thought disorder, delusions and lack of insight.