Finally, Goldberg & Zipursky acknowledge a fourth sense of “duty” – the “exemption”
sense – that aligns with Posner’s policy-based understanding that, in the nineteenth and twentieth
centuries, “as liability for negligence expanded, the judges felt a need to place limitations on its
scope and to rein in juries, and the concept of duty was revived to name some of these limitations and to exert some control over juries.”