Overconfidence and the Forgotten Unknowns: Case Studies from Science, Conspiracy, and Theology

Case Studies from Science, Conspiracy, and Theology Overconfidence in human reasoning often stems from neglecting the vast space of unconsidered explanations. This paper argues that rational belief requires preserving explicit probability reserves for unknown or unimagined possibilities, a principle deeply rooted in Bayesian epistemology. While formal treatments of imprecise or graded credences are well established (de Finetti, 2017; Joyce, 1998, 2009; Pettigrew, 2016; Walley, 1991), comparatively little attention is paid to how the absence of such reserves distorts inference in domains of deep ignorance. Case studies show how theology prematurely shifts credence to "God did it," how conspiracy thinking collapses uncertainty into binary narratives, how pre-scientific cultures attributed natural phenomena to supernatural agents, and how medicine, technology forecasting, and economics neglect disruptive unknowns. Across these domains, the forgotten unknowns foster premature closure and inflated certainty. By linking psychological research on motivated reasoning and conspiracy ideation (Kunda, 1990; van Prooijen & Douglas, 2013) with the Bayesian requirement to allocate probability mass to unmodeled hypotheses, the paper articulates a unifying epistemic norm: rational inquiry demands humility, explicit reserves for the unknown, and resistance to the illusion of decisiveness.