 For some one-factor theorists (Maher 1974), the delusion is a reasonable hypothesis given the strangeness of the experience, or the strange experience is in a sensory modality or at a processing stage where further reality testing is not available (Hohwy and Rosenberg 2005). But other one-factor theorists (e.g. Gerrans 2002a) argue that, although it may be reasonable at first to articulate a delusional hypothesis to explain unusual experience, it is not rational to maintain the delusional hypothesis in the face of counterevidence. Recent defences of the one-factor theory have emphasised that cognitive features in people who develop delusional beliefs are within the normal range and there is no need to postulate any reasoning deficit to explain delusion formation (Sullivan-Bissett 2018, 2020).