This paper starts from an observation of our practices: when people are ascribed delusional beliefs or conspiracy beliefs, they tend to be excluded from shared epistemic projects relevant to the content of their beliefs. What might motivate this exclusion? One possibility is that delusional beliefs and conspiracy beliefs are considered as evidence of irrationality and pathology, and thus endorsing them suggests that one’s epistemic agency is compromised, at least in some contexts. One common argument for the irrational and pathological nature of delusional beliefs and conspiracy beliefs lies in their being the outputs of faulty cognition. There are some areas of overlap in the cognitive antecedents of delusional beliefs and conspiracy beliefs as identified in the empirical literature. For instance, some biases and thinking styles have been correlated either with the adoption of delusional beliefs and conspiracy beliefs, or with the strength of conviction in such beliefs. The paper challenges the claim that, if delusional beliefs and conspiracy beliefs are the outputs of biased cognition, then it is justified to exclude people endorsing delusional beliefs and conspiracy beliefs from epistemic projects relevant to the content of their beliefs. The relevant biases and thinking styles are widespread in the non-clinical population, do not need to be part of a dysfunctional cognitive process, and can be adaptive in some contexts.