Kant’s Doctrine of Right: A Commentary by B. Sharon Byrd and Joachim Hruschka, Cambridge University Press, 2010.
B. Sharon Byrd and Joachim Hruschka bill their new book on Kant’s legal philosophy as a commentary but it is really much more than that. It is an authoritative and comprehensive systematization of Kant’s legal philosophy. What makes it a commentary is that the authors deal with all of the central ideas in Kant’s Doctrine of Right rather than just selecting those which fit their thesis. The authors argue that Kant is the first to present us with “one single model designed to ensure peace on the national, international, and cosmopolitan levels.” (1) This is an ambitious project and only a few political philosophers have followed Kant in seeking a complete theory along these lines. Hegel is an obvious example but few 20th Century theorists come to mind.
Such a theory requires sound philosophical footing and one of the achievements of Byrd and Hruschka’s commentary is that they are particularly strong on the philosophical foundations of Kant’s system, both with regard to how the legal theory relates to the moral theory and on how the overall structure of law relates to the different concrete legal spheres. These are the elements that I will concentrate on in this review.
A perennial problem in Kant scholarship has been the question of how Kant’s legal and moral philosophies relate. Kant characterizes the universal law of right thus: “Act externally so that the free use of your choice [can] coexist with everyone’s freedom according to a universal law”. (10, Akademie Ausgabe (AA) 5:231) The problem is that while the categorical imperative (“Act only in accordance with that maxim through which you can at the same time will that it become a universal law.” (AA 4:421)) applies to purely rational beings (who are not affected by their bodily conditions) the universal law of right has to take our embodiment into account because it deals precisely with the external relations between people. The question thus becomes: how is the moral law which applies to humans qua purely rational beings related to humans qua rational embodied beings? It may be that, as some commentators have urged, our embodiment cannot play any role in the specification of actual human laws. (This is Arthur Ripstein’s position, whose Force and Freedom I reviewed in this space a year ago. http://www.concurringopinions.com/archives/2010/03/book-review-ripsteins-force-and-freedom-kants-legal-and-political-philosophy.html) Or it may be, as H. L. A. Hart has argued, following Hume, that the specific embodiment does play an important role in the sorts of laws we legislate for ourselves. This is the gist of Hart’s giant crab example in “Positivism and the Separation of Law and Morality” (Harvard Law Review, 1958, 623).