Delusion

In a clinical context, delusions are symptoms of a number of psychiatric disorders including schizophrenia and dementia, manifesting as beliefs that are implausible and resistant to counter-evidence. In the philosophical literature, the nature of delusions (what they are) and their formation (what causes them) have been examined with increasing interest. Different arguments for and against delusions being regarded as beliefs have been put forward, and both the doxastic and the anti-doxastic camp capture some distinctive and puzzling features of delusions. The one-factor theory, the two-factor theory, and the prediction-error theory constitute distinct attempts to describe the causal mechanisms responsible for the formation of delusions and have implications for the management and treatment of delusions in clinical practice. The lively debates surrounding the nature and the causal history of delusions have also shed some light on standard issues in the philosophy of mind, such as what conditions a report needs to satisfy to be regarded as a belief report, and how experience and reasoning interact in generating of hypotheses that can then be accepted as beliefs.