<p>This paper explores the legal relevance of delusions in determining criminal responsibility. We argue that although delusions may be relevant in assessing capacity for criminal responsibility, the specific content of delusional beliefs should not form the basis for judgments of blameworthiness. The analysis takes the Anglo-American criminal law tradition as its starting point, focusing on the general structure of the M’Naghten rules rather than jurisdiction-specific interpretations. Courts sometimes treat the content of delusional beliefs as legally significant, asking whether the defendant’s conduct would be justified if those beliefs were true. We show that this approach presents serious conceptual and practical difficulties. It requires counterfactual reasoning about imagined realities, thereby shifting the assessment of responsibility from the defendant’s actual impairments to a hypothetical reconstruction of their worldview. We argue that this method conflates justification with excuse, demands obscure counterfactual reasoning about fictional realities, and is ill-suited to bizarre delusions that lie outside any coherent legal or moral framework. It risks producing inequitable outcomes, favouring defendants whose delusions can be rendered intelligible within existing justificatory doctrines while disadvantaging those with more incomprehensible psychoses.</p>