Delusional inference has been increasingly understood in terms of Bayesian updating. In our paper we critically evaluate an influential Bayesian model of delusional inference put forward by Coltheart, Menzies, and Sutton (2010), which we call, for simplicity, ‘the Coltheart model’. The Coltheart model has been developed with specific reference to the Capgras delusion, the belief that a person or persons dear to the deluded individual have been replaced by identical or nearly identical imposters (Capgras and Reboul-Lachaux, 1923).
In the last decade, many theorists have pointed to the use of Bayesian framework for modelling delusional inference, with the debate revolving around the number of factors necessary for delusion formation, and the similarities and differences between the available models (e.g., Coltheart et al., 2010; McKay, 2012; Bortolotti and Miyazono, 2015; Miyazono et al., 2015; Miyazono and McKay, 2019).
By contrast, we focus on the question of compatibility between, on the one hand, the Coltheart model, and on the other hand, explanationist and endorsement accounts of delusion formation. Strictly speaking, the Coltheart model is not a Maher-type explanationism, at least if one treats experience as by definition conscious. It does, however, conceptualise delusions as hypotheses serving an explanatory function.
Because of that, the Coltheart model has been interpreted as a modern version of explanationism (Parrott, 2019; Young, 2014). We argue, however, that an explanatory function as understood here is no less compatible with an explanatory picture than an endorsement one. If that is correct, the mere presence of inference in delusion formation is not sufficient to discriminate between explanationist and endorsement accounts.