The purpose of my previous post on this subject was not to demonstrate that interpersonal utility comparisons (IUCs) are invalid. The purpose was to explain how commonplace observations that seem like IUCs (e.g., “My daughter will enjoy this baby doll more than my son”) might not really be IUCs after all, but instead a species of intrapersonal utility comparison. In other words, I was responding to a common argument in favor of IUCs, not positing an independent argument against them.
But I made the mistake of beginning that post by describing my attitude toward IUCs, and many (in the comments and elsewhere) took that description as a justification. In this post, I’ll take the question head on. Why do I think IUCs aren’t valid?
The most important point is utility, as the term is used by economists, is not synonymous with happiness or pleasure-net-of-pain. If it were, then I’d concede that we might be able to find some kind of scientific and interpersonally comparable measure of it, such as dopamine levels (or some other chemical aspect of the brain). But utility is used more broadly to mean satisfaction of preferences, where preferences are understood to include all sorts of values that might contradict or even transcend the dictates of mere pleasure and pain. And for this kind of utility, which is the kind I think matters, it’s far from clear that a single brain-chemical or brain-activity measure exists. People can value things in spite of, or even because of, the pain or self-denial involved. Will Wilkinson does an excellent job of making this point. Will gives the example of a fighter at the end of a brutal battle, in substantial pain and on the verge of death, who nonetheless thinks there is value in having fought well. I would add the example of a man who abstains from sex for moral reasons, even though he would derive substantial pleasure from having more sex.
In order to believe there is (or could be in principle) a scientific measure that encompasses both the pain from stab wounds and the value-satisfaction of having fought well – both the forgone pleasure of sex and the value-satisfaction of not being promiscuous – you have to believe that all values are “cashed out” in terms of the very same chemical(s) as simple pleasure and pain. Let’s say you think utility can be measured in dopamine levels. Then you have to think the value the fighter places on having fought well (perhaps for a good cause!) creates doses of dopamine that more than compensate for the physical pain of battle. And you have to think the abstainer’s valuation of non-promiscuity creates enough dopamine to make up for the forgone dopamine from sex. To paraphrase Will, you have to think that being good also feels good.
To be clear, I’m not saying value-motivated action lacks a chemical cause. It is brain activity, after all, so it must have some kind of neuro-chemical explanation. But I’d be very surprised to find it was the same chemicals and processes as those that correspond to the pain from stab wounds or pleasure from sex.
(Indeed, I wonder whether even raw pain and pleasure involve the same chemicals and processes. When someone experiences something that involves both pain and pleasure, they really experience both, not some net effect of pleasure minus pain. Doubt it? Ask someone who’s into sadomasochism. They don’t do it despite the pain, but in part because of it. Actually, I feel somewhat the same way about getting a back massage. I enjoy it most if my muscles are sore enough to hurt a little when they’re massaged. Does that make me a freak?)
In any case, different people have different lifeplans (Will’s terminology), which are essentially patterns that they wish to achieve. Such patterns may include the achievement or avoidance of hedonic pain and pleasure, but they consist of other things as well. “Utility” means congruence of one’s behavior and/or situation with the pattern. Now, what is the scientific unit for congruence, or lack thereof? I don’t think such a unit exists. Patterns cannot be compared in the same way that quantities can. Moreover, outcomes can be inconsistent with patterns in different ways, most likely resulting in different sorts of dissatisfaction in the brain. Thus, any attempt to measure the effect of incongruence will likely result in multiple measures. Imagine, for instance, the effect of our sexual abstainer giving in to temptation and having an orgasm; he may simultaneously experience ecstasy (perhaps measurable on one dimension in one kind of unit) and moral guilt (perhaps measurable on another dimension in another kind of unit).
Now, it might seem I’ve made the case against intrapersonal utility comparisons, since my argument seems to hinge on a kind of incommensurability of different experiences within a single brain. If so, that would certainly do the job: if intrapersonal comparisons don’t work, a fortiori interpersonal comparisons don’t either. But while jettisoning intrapersonal comparisons might be the correct conclusion, it isn’t strictly necessary for the argument. From introspection, it seems that somehow we negotiate our conflicting impulses, and we arrive at some notion of what kind of pattern we wish to achieve. That pattern might not correspond to any single measurable aspect of the brain, such as the amount of some chemical. It might, and I strongly suspect does, correspond to a kind of balance (or imbalance?) of different motivational forces, and the balance differs from person to person.
The result is that individuals arrive at various desired patterns, which we call preferences, whose satisfaction can only be understood in terms of their congruence with outcomes. We can say that certain changes will assist the achievement of one individual’s pattern while undermining the achievement of another’s, but we have no unit in terms of which we could say the increase in congruence for the former is “bigger” than the reduction in congruence for the latter.