The papers included in the thesis, and summarized in this covering document, were selected, in discussion with my supervisor, Dr. Roessler, from papers I have published in the philosophy of psychiatry. In parallel to this philosophical work, I have worked clinically as a psychiatrist and academically as a research psychiatrist. My clinical work has largely been working with Early Intervention Services, both in South London and in Coventry and Warwickshire, and this work has been acting as a psychiatrist in clinical (...) teams who work with young people who may either be at risk of developing a psychotic illness, or are in the earliest stages of such an illness. My empirical work has been in the same clinical group and has used functional neuroimaging and cognitive neuropsychology to characterize those at risk of psychosis and to chart the onset of psychosis and the formation of delusions. As required by the university guidelines, a full list of publications, both empirical and philosophical, is detailed in appendix 1. The papers included in the thesis hence parallel many of these clinical and empirical interests: papers 2 and 4, in particular, examine the role neuroimaging may play in studying delusions and relate the prodromal phase of psychosis to both the neurodevelopmental and continuum models of psychosis. Paper 3 is one of two papers written with Lisa Bortolotti drawing on Richard Moran’s work and examining delusions. Paper 1 is perhaps the paper least connected to my empirical and clinical work as has a wider focus and tries to examine what mental illnesses are and to begin to describe a position Lisa Bortolotti and I later expanded on and referred to as ‘psychological realism’, with Paper 2 being a case example of this account being applied to a particular area of psychopathology, namely delusions. The papers form a progression with Paper 1 outlining a general conception of mental disorder, Paper 2 being a case study of this approach specifically in the area of delusion. Paper 3 takes the example of thought insertion and develops ideas from Paper 2 that reason giving is a crucial feature that helps highlight what is pathological about certain experiences. Paper 4 brings together the philosophical concerns regarding a wholly neuroscientific conception of psychopathology, and how this is of clinical and scientific relevance when we use psychopathology to demarcate the various stages of psychotic experience and illness. (shrink)