We would agree that deficits of theory of mind may prove one mechanism that differentiates pathways to delusional belief rather than hallucinations. Indeed, a symptom-specific approach to research across diagnostic groups is increasingly called for. National Institute of Mental Health Research Domain Criteria encourage this approach, and there is already a volume of research on the causes of hallucinations, and childhood experiences therein. ^{Reference Insel, Cuthbert, Garvey, Heinssen, Pine and Quinn1–Reference Modinos, Costafreda, van Tol, McGuire, Aleman and Allen3} Persecutory delusional beliefs – and a specific neurobiology for these – have also been investigated, with significant results centring around salience, prediction error and social cognitive processing. ^{Reference Upthegrove, Ross, Brunet, McCollum and Jones4–Reference Corlett and Fletcher6} Further focus on the distinction between primary and secondary delusions, and those with content outside the persecutory, is also needed.