The Australian philosopher Philip Gerrans ambitiously tries to provide a general theory about the formation of delusions that should enclose neuronal, cognitive and phenomenological levels of description. His theory is defined as narrative and it is grounded on the so called “default thoughts”, that consist in simulations, autobiographical narrative fragments produced by the Default Mode Network (DMN). The DMN is a powerful simulation system that evolved to allow humans to simulate and imagine experiences in the absence of an eliciting stimulus. Such imaginative/simulative process is precariously disciplined by the Self’s demands of narrative coherence. The Author’s aim is to waive the notion of belief and the causal role played by the impairments of fixation-beliefs system in the onset of delusions, as predicted by the principle doxastic theories.