Monothematic delusions and the nature of belief

In this thesis I argue that our philosophical account of the nature and norms of belief should both inform and be informed by our scientific understanding of monothematic delusions. In Chapter 1, I examine and criticise standard attempts to answer the question “What is delusion?” In particular, I claim that such attempts are misguided because they misunderstand the kind of term that “delusion” is. In Chapter 2, I look at the nature of explanation in psychology and apply it to delusions. In particular I look at the constraints on a successful explanation of a person’s psychological state in terms of brain damage or dysfunction. I then propose, in Chapter 3, a way of understanding how delusions of misidentification arise. In particular, I criticise the standard view that they are formed via inference (in the relevant sense of “inference”) on the basis of anomalous experience. I draw on empirical work on object and individual tracking, on dreams, and on the Frégoli delusion, and argue that inference is not only un-necessary, but is actually often bypassed in humans, for judgments of identification. The result is a non-inferential file-retrieval view. On certain views of belief, this would mean that the Capgras delusion lacks the right functional role to count as a genuine belief. In Chapter 4, I criticise such views of belief, and put forward a “downstream only” view. Roughly, something is a case of believing if and only if it disposes people to act in certain ways. I defend such a view against two serious and influential objections. In Chapter 5, I ask whether this means that the Capgras delusion can therefore safely be called a belief. I argue that there is a risk – even if one accepts the downstream only view of belief – that it still won’t count as a belief, as a result of the subject’s “incoherence” or “agentive inertia.” However, I then distinguish egocentric from encyclopaedic doxastic states. This opens the possibility that one can truly say that the subject has the egocentric belief, “This man is not my father”, but may fail to have the encyclopaedic belief, “My father has been replaced by an impostor”. It also demonstrates that the question “Are delusions beliefs?” has been approached in an unhelpful way by the main participants in the debate. This thesis is important because it shows the extent to which real-world phenomena can inform and be informed by central philosophical notions like belief. More precisely, it shows that the most plausible way of accounting for monothematic delusions involves abandoning both a strong normativism, and a discrete representationalism, about belief