Garety & Freeman present a timely review on the nature of delusional experience. ^{Reference Garety and Freeman1} Their conclusion regarding the need to focus on individual features of psychosis seems apt. The presented overview of cognitive and affective mechanisms influencing delusion development seems, however, to overlook an essential component of delusional experience; that psychotic symptoms, including delusions, at their heart represent a failure of reality testing.

The description of jumping to conclusions, together with the probabilistic reasoning task methodology, appear to rely on a logical chain of thought progression and conclusion - what Campbell has referred to as an empiricist understanding. ^{Reference Campbell2} This approach, however, does not take into account the nature of conclusions reached in delusional belief. Conclusions reached on seeing two, or fewer, coloured counters seem quite distinct from classic examples of delusional perception: ‘I saw the traffic lights turn green and realised that the world would end’. Campbell’s alternative rationalist approach presents the person with delusions as having experienced a complete rearrangement of their framework propositions, or underlying background world beliefs. Such a fundamental shift in a world-view model can go some way to explaining the fantastical nature of conclusions reached, or the failure of reality testing present in psychosis.

Campbell’s arguments have not gone unchallenged. ^{Reference Bayne and Pacherie3} However, what they do highlight is a need for careful consideration as to the manner in which delusional beliefs are formed. Garety & Freeman describe the psychoanalytic thinking in relation to defence mechanisms in the development of persecutory delusional belief. Psychotic defence concepts, wherein the individual denies or distorts reality to defend against trauma, provide one possible lens through which psychotic experiences can be viewed. ^{Reference Hingley4,Reference Martindale and Summers5}

Garety & Freeman’s conclusion relating to the infancy of research into the nature of delusion, and its having been overshadowed by focus on the larger concept of schizophrenia, highlights the need for further research. Future research will need to provide some account for the distortion of reality that seems central to the experience of psychosis.