Book Review: How Hume and Kant Reconstruct Natural Law: Justifying Strict Objectivity without Debating Moral Realism

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Westphal Kenneth., How Hume and Kant Reconstruct Natural Law: Justifying Strict Objectivity without Debating Moral Realism Oxford: Oxford University Press, 2016 Pp. 208 ISBN 9780198747055 (hbk) $65.00

The subtitle of this book is suggestive, for one can avoid debating moral realism in several ways. Hume and Kant might first be understood as having avoided debating moral realism because the term was not invented for close to two centuries after they wrote. But of course what we call the ‘moral realism’ debate does apply to their theories despite the novel terminology. Or secondly one might invoke a claim that moral realism is a meta-ethical issue on a distinct plane from normative ethical considerations, and hence the subject of an entirely different kind of analysis that abstracts from, or is even unrelated to, particular normative theories. But this claim, although promoted by the initial twentieth-century advocates of what came to be called meta-ethics, is certainly implausible because some issues, such as the status of reason as a source of moral law or the role of values that depend on human nature, are not exclusively metaethical or normative, particularly in a Kantian theory. Or thirdly one might avoid the debate about realism by employing a narrow focus in reconstructions of political philosophy proper, discussing the foundational questions that involve realism somewhere other than in that specific discussion of political philosophy. In that case only the narrow normative claims and not the complete theory are presented without debating moral realism. Those who are concerned with political philosophy might in this case simply take for granted an answer to the realism question, or bracket the debate for the purpose of answering specific questions in political philosophy first. The issue of realism is then handled in the more extensive general theory, or perhaps in some foundational discussion. I take this third option to describe the way that Hume and Kant might be understood to present political philosophies that do not get entangled with issues about realism.

Kenneth Westphal has none of these in mind but instead holds that what he takes to be Hume and Kant’s shared framework – ‘Natural Law Constructivism’ – is completely worked out in a way that resolves all the issues about identification, knowledge and justification...