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Derek Parfit is one of my favorite philosophers, and favorite writers at that, so for many years I have been looking forward to his next book, which is now out.  The main argument is that rule consequentialism, properly understood Kantianism, and contractualism all can be understood as a broadly consistent moral theory, all climbing up the same mountain from different sides.

The text is recognizably Parfit, but I am not convinced by its major arguments, and I also believe the Parfitian method — any reader of him will understand this reference — does not succeed in all of the new areas under consideration.

The philosophical patron saints of the book are Kant and Sidgwick, and I would suggest also Bloomsbury.  Parfit is an extreme rationalist and he thinks (hopes?) we can find, and agree upon, the right answers to moral questions.  (At the same time he deeply fears that we cannot, and he is a philosophic conservative as Keynes was.)  What’s missing is Hume, not the Hume of is-ought worries but the Hume who came to terms with the tensions between the arguments of philosophy and the experience of everyday human life.

My favorite features of the Parfit book include the early comparison of Kant and Sidgwick and the general concern with the frequency and intensity of moral disagreement.

Parfit at great length discusses optimific principles, namely which specifications of rule consequentialism and Kantian obligations can succeed, given strategic behavior, collective action problems, non-linearities, and other tricks of the trade.  The Kantian might feel that the turf is already making too many concessions to the consequentialists, but my concern differs.  I am frustrated with this very long and very central part of the book, which cries out for formalization or at the very least citations to formalized game theory.

If you’re analyzing a claim such as — “It is wrong to act in some way unless everyone could rationally will it to be true that everyone believes such acts to be morally permitted” (p.20)  — words cannot bring you very far, and I write this as a not-very-mathematically-formal economist.

Parfit is operating in the territory of solution concepts and game-theoretic equilibrium refinements, but with nary a nod in their direction.  By the end of his lengthy and indeed exhausting discussions, I do not feel I am up to where game theory was in 1990.

I read the standard game-theoretic results as implying that ethics is a far more indeterminate enterprise than Parfit might like to see.  Any particular specification of rule consequentialism tends to require increasingly baroque refinements to cover all the different possible kinds of situations.  At the end we’re not left with much in the way of a rule at all, other than a general injunction to tell people to do something good and then to rejigger the rule itself, or complicate it with more contingencies, to cover the required ground.

To pose a simple example: “maximize your marginal impact” won’t as an injunction address a lot of environmental problems.  “Maximize your average impact” fails in cases where you are truly decisive.  What might other more complex rules be, and what are the expectations those rules are making about the behavior of others, what you infer from their behavior, what they infer from your inference, and so on.  The path out of these boxes takes us very far away from a rules concept that say Sidgwick might have found intuitive.

Hume has been locked out of the room and he is not allowed to re-enter in the form of Parfit having a dialogue with Cho and Kreps.

Now maybe, just maybe, that game-theoretic messiness does not have to be fatal for rule-consequentialism.  Still, I propose a rewrite.  Cut or severely limit the hundreds of pages on this topic, start with what game theory already is showing, describe that mess in philosophic, conceptual terms, and then consider whether that mess is compatible with the analogous messes found in Kantianism and contractualism,  Maybe it can be shown that they are (broadly) the same mess.  Nonetheless, such a collection of messes may be surrounding the same mountain but they will not scale it and Parfit would have to gaze once again into the abyss of, what is to him, ethical nihilism.  (Cut back to David Hume for a different attitude.  Perhaps Parfit’s very strong philosophic and personal desire to succeed and solve the whole problem draws him from the path that will get us up the mountain some small degree.)

For these reasons I see the biggest and most central part of the book as a failure, possibly wrong but more worryingly “not even wrong” and simply missing the questions defined by where the frontier — choice theory and not just philosophic ethics — has been for some time.

On other points, the criticisms of subjective and desire-based theories are good, but I view Parfit’s conclusions as already having been established.

The talk of Kantian dignity, and of “treating people as a mere means” I do not think can be well-defined.  I kept on wanting to see the Marginal Revolution (the real one, the 1871 one) inform this discussion.

I very much agree with Parfit’s argument that no one — not even evil people — should deserve to suffer.  I also agree with Parfit’s notion of the irreducibly normative.

Until the material on consequentialism is nailed, I don’t think the integration with contractualism can work.

I would describe the Parfitian method as “the postulation of bold, minimalist claims, explored by the use of brilliant hypotheticals and counterexamples.”  In Reasons and Persons the Parfitian method works because the potential for philosophic vagueness is limited by the vividness of the counterfactual (or real world) examples.  Most readers of that book are still thinking about split brains, the Repugnant Conclusion, and Future Tuesday Indifference, among numerous other examples.  You could question whether all of the terms were pinned down rigorously, but you still knew that the thought experiment was making you rethink some of your priors.  In the subject areas of On What Matters the semantics are too slack, too open to multiple interpretation, and too many of the central concepts cry out for formalization.  There are not compelling new metaphors and examples to pin down the discourse.  Parfit’s greatest strength is as an imaginer, often outside of traditional philosophic dimensions, and yet here he is so concerned with justifying his disagreements with his peers and colleagues.  Their ghosts and comments and discourses are shackling him, and if you visit the best pages of Reasons and Persons you will see they hardly mention the names of other philosophers at all, much less current philosophers.

I do not wish to put you off Parfit.  He is a philosopher of major importance and, non-trivially, one of the most philosophical philosophers, perhaps ever.  He lives, thinks, feels, breathes, and exudes philosophy in a way which is, in and of itself, a major contribution to human thought and being.  Reading him is an unforgettable and illuminating experience.  His best arguments have great real world import.

It is stunning to read the last three pages of the preface, which list everybody who gave him comments.  It’s a long list, but I’m not sure it was the right list to have chosen.

Addendum: Here is Peter Singer’s review.  Here is a review from Constantine Sandis.