Some belief systems postulate intelligent agents that are deliberately evading detection and thus sabotaging any possible investigation into their existence. This may give rise to an ‘epistemic black hole’, as we call it: a complex of beliefs that is extremely attractive but hard to escape from. We describe the outlines of epistemic black holes in a range of different domains: politics, history, psychology, and religion. Because of their extreme resilience to counterevidence, such belief systems suffer from a recurring problem of arbitrariness and proliferating alternatives, and they tend to develop and evolve in analogous ways. Shedding light on how epistemic black holes function can protect us against their allure