Why do we punish negligence? Leading accounts explain away the punishment of negligence as a consequence of other, well-known phenomena: outcome bias, character inference, or the volitional choice not to exercise due care. Although they capture many important cases, these explanations fail to account for others. We argue that, in addition to these phenomena, there is something both fundamental and unique to the punishment of negligence itself: People hold others directly responsible for the basic fact of failing to bring to mind information that would help them to avoid important risks. In other words, we propose that at its heart negligence is a failure of thought. Drawing on the current literature in moral psychology, we suggest that people find it natural to punish such failures, even when they don’t arise from conscious, volitional choice. Then, drawing on the literature on how thoughts come to mind, we argue that punishing a person for forgetting will help them remember in the future. This provides new insight on the structure and function of our tendency to punish negligent actions.