In this essay I strive to exorcize an epistemological demon, the demon of closure. The demon has long haunted theology to devastating effect. It makes chimeric concerns appear urgent, encourages false trajectories of inquiry, fosters unnecessary fears, propagates intolerance, and instigates violence. I begin with Charles Taylor's exposure of the demon in the context of philosophy's free will/determinism debate. Second, I sketch the demon's haunting of the patristic trinitarian and christological controversies, and its recent haunting of theology vis-à-vis the problem of evil. Third, I delineate and champion what I call ‘Chalcedonian reason’ (Taylor calls it ‘revised transcendental reasoning’). Chalcedonian reason emerges in the wake of the exorcism of the demon of closure (and involves significant revision of modern ideas about rationality). I argue that Chalcedonian reason is as old as Job, emerges amazingly triumphant, if unrecognized, in the patristic period, fosters humility and openness to the Spirit, and is wonderfully consonant with Christian theology and spirituality.