This Essay deveopes an ideal of public legal reason - a normative theory of legal reasons that is appropriate for a society characterized by religious and moral pluralism. One of the implications of this theory is that normative theorizing about public and private law should eschew reliance on the deep premises of deontology or consequentialism and should instead rely on what I shall call public values - values that can be affirmed without relying on the deep and controversial premises of particular comprehensive moral doctrines.
The ideal of public legal reason is then applied to a particular question - whether welfarism (a particular form of normative law and economics) provides the sort of reasons that appropriate for legal practice. The answer to that question is no - to the extent that welfarism contends that the normative assessment of legal policies should rely exclusively on information about individual preferences, welfarism relies on deep and controversial premises of consequentialist moral theory that are fail the test of public reason. The Essay also investigates the thesis - advanced by Louis Kaplow and Steven Shavell - that any fairness principle (a nonwelfarist method of policy assessment) can violate weak Pareto (making everyone worse off). Whatever the implications of Kaplow and Shavell's argument, it does not show that welfarism can provide public legal reasons. The essay concludes that law's justifications should rely on normative principles that are accessible to reasonable citizens, whether they are theists or atheists, deontologists or consequentialists, moral philosophers or economists. Law's deliberations should be shallow and not deep. Law's reason should be public.