The planning theory and natural law

The practical, normative dimension of planning is a plausible source of the ‘family resemblances’ noted by a number of legal theorists between Scott Shapiro’s Planning Theory and natural law jurisprudence. Foremost among these resemblances is Shapiro’s contention that the law, necessarily, has a moral aim. The moral aim thesis is at first glance surprising given Shapiro’s intention to defend exclusive legal positivism and unequivocal rejection of what he takes to be the core commitments of natural law theory. Shapiro’s claim, however, is that although the law necessarily has a moral aim, this does not entail that it is successful in satisfying that aim. In order to assess this thesis, it is helpful to compare the Planning Theory with contemporary natural law approaches. Bringing Shapiro’s Planning Theory into dialogue with contemporary natural law theories can demonstrate some of the Planning Theory’s weaknesses as an alternative explanation of the ultimate grounds of the authoritativeness of legal norms. Some of these weaknesses, moreover, are instructive beyond the specific contours of the Planning Theory insofar as they generalise to other legal positivist approaches. In section one I consider Shapiro’s treatment of the so-called ‘Possibility Puzzle’ regarding the grounding relation between authoritative norms and legal authority. Shapiro’s denial of the capacity of earlier jurisprudential theories to resolve this puzzle overlooks what is – I suggest – a plausible solution developed by John Finnis on the basis of Joseph Raz’s theory of practical reason and norms. Section two then demonstrates why Shapiro’s attempt to combine a robust construal of the social facts thesis with a commitment to the thesis that law necessarily has a moral aim is ultimately unsuccessful.