The Impossibility of Interpersonal Utility Comparisons

This is a linkpost for The Impossibility of Interpersonal Utility Comparisons by Daniel M. Hausman, which was originally published in Mind in 1995. It is freely available on Sci-Hub. Below is a summary from Claude Opus 4.8 High. Daniel said "I think the summary is accurate". I also believe the summary is accurate based on my read of the article. I used the following prompt. "Hi. Make an in-depth summary of the article "The Impossibility of Interpersonal Utility Comparisons", which I send attached".

The central thesis and argument structure

Hausman targets the preference-satisfaction theory of well-being — the view that a person's welfare consists in the extent to which their preferences are satisfied (where a preference is satisfied when the world is as the person prefers, independently of any accompanying feeling of satisfaction). His conclusion is that this theory must be rejected, because it cannot underwrite the interpersonal comparisons that moral theory requires.

The argument is a modus-tollens-style reductio [ad absurdum] in three premises [context]:

1. If welfare is the satisfaction of (actual or rational) preferences, then interpersonal utility comparisons cannot be made in a morally acceptable way.
2. If such comparisons cannot be made acceptably, then utilitarianism and virtually all other moral views are untenable.
3. Therefore, either those moral views are untenable, or well-being is not the satisfaction of preferences.

The essay concentrates almost entirely on defending premise 1. Premise 2 rests on the thought that most moralities require comparing the good of different people for purposes of benevolence or justice. Throughout, Hausman insists on taking the slogan "utility just represents preference" literally: utility is nothing more than an index of location in an unchanging preference ranking, not a separate good that people possess in varying intensities. He assumes preferences are consistent (an ordering) and unchanging, since relaxing either only makes comparisons harder.

A key framing distinction: an interpersonal comparison here is a comparison of how well satisfied Ira's and Jill's preferences are, not of how well off Ira and Jill are as persons — not a comparison of their mental or physical states, but of the extent to which the world matches what each prefers.

Section 1 — Ordinal utility

On the standard ordinal conception, only the ordering of utility numbers carries information; differences and ratios are arbitrary. Hausman grants immediately that ordinal unit (difference) comparisons are impossible — but notes this has nothing to do with interpersonality, since utility differences are meaningless even intrapersonally. This already dissolves Nozick's "utility monster" and Ira's claim to greater "sensitivity": with only ordinal information, a global claim to always gain more utility is simply incoherent.

The harder case is ordinal level comparisons. Superficially, Jill is better off than Ira if her preferences are satisfied to a greater extent — i.e., if she sits higher in her ranking than he sits in his. But Hausman attacks the notion of comparable "location" in an ordinal ranking. There are no units of "distance" within an ordinal ordering. Attempts to give location content — e.g., counting alternatives above and below an option — fail: the individuation and counting of alternatives is arbitrary, and once lotteries are admitted there are infinitely many alternatives above and below any intermediate option. So there is no non-arbitrary fact about whether a position in one ranking is "higher" than a position in another.

He then adds a second, independent objection: even if such counting could be made to work, it would be morally irrelevant, because the count depends on incidental facts like what each person happens to be able to imagine. Either way, ordinal level comparisons of the intermediate positions are unavailable.

Section 2 — Extended sympathy fails to rescue

The main proposed rescue is Arrow's "judgments of extended sympathy": an extended utility function V over person-state pairs, so that Ira-with-x beats Jill-with-y iff [if and only if] V(Ira,x) > V(Jill,y). Hausman asks what fills the blank in "___ prefers Ira-with-x to Jill-with-y." No one's actual preferences will do: whether Ira is better off than Jill shouldn't depend on what bystanders happen to prefer; people may prefer to be Jill for reasons (nobility, etc.) unrelated to who is better off; and people who prefer Ira's state because they judge him better off cannot ground that judgment in the preference — the belief explains the preference, not vice versa.

On the standard reading, extended-sympathy judgments express "impersonal" preferences realized by imaginatively taking on Ira's, then Jill's, preferences and asking how well one's imagined preferences would be satisfied. This is supposed to be underwritten by psychological laws (V summarizing what causal factors produce which preferences, with Uⱼ(y) = V(rⱼ,y)). Hausman's objection: what one needs is not laws relating how preferences are acquired to causal factors — those we roughly have — but laws relating preference structures and world-states to some impersonal measure. There is no evidential basis for the latter. It can't come from a theory of mental states (welfare is supposed to be preference satisfaction, not feeling), nor from any substantive theory of the good (those have been set aside by assumption), nor from comparisons of well-being (which is exactly what's in question and would make the account circular), nor from actually expressed preferences (already ruled out). So extended sympathy provides no way to determine whose preferences are better satisfied.

Section 3 — Conclusion on ordinal levels

Within a purely ordinal index there are at most three comparable locations: bottom, top, and undifferentiated "intermediate." No evaluative commitment to fairness or equality can generate comparisons among intermediate locations. Robbins was therefore right to deny ordinal level comparability — but for the wrong reasons (not because of introspection problems or because such comparisons are value judgments; value judgments can be inconsistent and are of no help). Hausman notes that people do make interpersonal welfare comparisons in ordinary life, but takes this as no embarrassment: there's little reason to think those everyday comparisons are comparisons of preference satisfaction, and the very fact that eminent theorists can't hold consistently to the preference view is itself evidence for that.

Section 4 — Cardinal utility and the zero-one rule (the positive core)

The striking move: adding cardinal structure changes nothing unless the cardinal index is bounded. If unbounded, the "distance" above and below any option is infinite for both people, and comparison remains impossible. But if preferences can be represented by a bounded cardinal utility function, unique up to positive affine transformation [context], then Hausman contends there is exactly one right way to compare — the zero-one rule: normalize each person's scale so that the top of their preference ranking = 1 and the bottom = 0, then compare the resulting ratios

$\frac{U_i\left(x\right)-min{U}_i}{max{U}_i-min{U}_i}\text{vs.}\frac{U_j\left(y\right)-min{U}_j}{max{U}_j-min{U}_j}$

His central and most provocative claim is that taking the preference view literally commits you to the zero-one rule — and crucially, this argument does not rest on any fairness premise (unlike the rule's usual defenders). The reasoning: to say Jill's bottom might be "lower" than Ira's bottom is implicitly to smuggle in some notion of utility beyond "extent to which preferences are satisfied." If both are at the very bottom, neither's preferences are satisfied at all — there is simply nothing there to be more or less of. He reinforces this with a change argument: if Jill's preferences shifted to become identical to Ira's while leaving her non-comparative welfare untouched, a definition of comparative well-being denying top/bottom equality would have to say her welfare both did and didn't change — a contradiction. Hence people at the top (or bottom) of their rankings must be equally well off.

He carefully distinguishes his rule from two lookalikes: it is not assigning 0 and 1 to the best/worst feasible options in a decision problem, and it is not Gauthier-style "relative concessions" in bargaining. The relevant scale is the person's full ranking over everything they've conceived. He concedes an awkward consequence — those good at imagining bliss come out worse off, those good at imagining misery better off — but argues this is an objection to preference-satisfaction views (or to using actual preferences), not to his account of how to compare given that view.

Section 5 — Why the solution has been missed

His eleven-word diagnosis: because theorists haven't taken literally the view that utility represents preference. The zero-one rule is old (Isbell 1959), but it has always been presented and attacked as a fairness device. Hausman reviews four critics — Hammond, Sen, Rawls, Griffin — and turns each objection against the preference view rather than against his rule:

• Hammond objects that normalizing an "undemanding" person's scale to match a "greedy" person's over-rewards the greedy under a 90%-of-max distribution. Hausman agrees it's unfair — but says this shows one should abandon the preference view, not the rule.
• Sen attacks both the fairness and the plausibility of the rule (noting rival normalizations, e.g., setting the sum of utilities to 1, and the wish to accommodate people with lower "capacity for satisfaction"). Hausman replies that the sum-based alternative doesn't track extent of preference satisfaction at all, and that Sen's plausibility worry presupposes utility is more than a preference index.
• Rawls (expanding Sen) says the rule implies all individuals have "similar capacities for satisfaction" and that great social utility comes from teaching people simple, easily satisfied desires. Hausman charges this conflates preference-satisfaction with mental-state views — the giveaway phrase being "easily satisfied." That someone with modest desires ends up "better off" is an objection to the preference view itself.
• Griffin says the rule is "just false" — we don't all reach the same peaks and valleys. Hausman: to say your top preference leaves you "higher up" than my top preference is to invoke elevation, i.e., some notion beyond preference satisfaction. If utility is only a preference index and both are perfectly satisfied, they must be equally well off.

Section 6 — Implications

The argument can be read two ways: as a new technology for making comparisons, or as a reductio of the preference-satisfaction conception. For actual-preference views, one must read it as a reductio: comparison requires a bounded cardinal representation (which few people's preferences even approximate — many can't be represented ordinally), and even where it works, the Hammond/Sen/Rawls/Griffin intuitions show that people at the same ranking-location are not intuitively equally well off. Hausman argues the same conclusion follows, if less obviously, for informed/rational-preference views: because extravagant or extremely modest preferences may fail to be "rational," the rule won't automatically recommend cultivating modest wants, so the objections are partly answered — but the rule remains ethically implausible and ordinal comparisons remain impossible. He also rebuts the economist's fallback that preference satisfaction is merely an empirical proxy for welfare: preference satisfaction is too hard to measure to be a good proxy, and if welfare is something else, economists owe an account of what that something is.

Section 7 — Objections and replies

Five objections, each turned aside:

1. Thermometer analogy (Sensat): chemists with uncalibrated thermometers normalizing freeze/boil points to 0–1 could say ethanol is "higher up its scale" than water, which sounds like an error since ethanol isn't hotter. Hausman: given their concept of "hotness" (relative location between freeze and boil), ethanol is hotter; the analogy shows one should develop a better concept, not that the zero-one rule misapplies the concept one has.
2. Can indices be added/subtracted? (Elster): yes, sometimes sensibly — e.g., ranking environments by percent of genetically maximal height or lifespan achieved, then summing or averaging across populations to compare countries. So difference-comparison worries don't defeat the rule.
3. Cross-category intensities (Broome): why say the most intense blue equals the most intense anger? Hausman: if "intensity" just means location in a cardinal ranking, the zero-one rule is right, and the two maxima are equally intense. What's odd is wanting to compare them at all — but he only claims to show how to compare if one wants to, not that one ought to.
4. Utility reflects rather than determines welfare (Railton): the judgment that Jill is higher in her ranking follows from her being better off, not the reverse. Hausman agrees about the direction of determination for a single person's own case, but points out that when comparing Jill-with-y and Ira-with-x, the rankings are already given; the interpersonal comparison doesn't constitute them, so we still lack a basis for the cross-person judgment.
5. Straw man — real comparisons use empathy, not preference-extent. Hausman: correct as description, but this supports his thesis, since it shows practitioners don't actually hold consistently to the preference notion they claim to endorse.

Section 8 — Conclusion

Two disturbing results: interpersonal comparisons of ordinal utilities are largely impossible, and for bounded cardinal utilities the zero-one rule is the uniquely correct method — yet it conflicts with our intuitive comparisons. Since interpersonal comparison is ineliminable in human life, and since the serious problems with "equally well off iff equally satisfied" give strong reason not to identify welfare with preference satisfaction, anyone assessing preference utilitarianism, refining benevolence, or understanding prudence must first be clear about what taking well-being to be preference satisfaction actually involves.