Thinking and Deciding

400 MORAL JUDGMENT AND CHOICE
must switch their utilities too.) Notice that when you do this, we are basically trying
to maximize their combined utility, as if we were applying MAUT (Chapter 14),
with each person providing one dimension of a decision involving two independent
dimensions.
Notice that the comparison is of differences or changes, not levels. All we need to
decide is whether John’s playing his music increases his utility more than it decreases
Judy’s. We do not need to decide whether John is happier or better off than Judy in
general. Likewise, in considering a tax on the rich to help the poor, we should ask
whether the decrease in utility for the rich is smaller than the increase for the poor.
For making the relevant comparison, we need not consider absolute levels of utility.
We are concerned only with the consequences of a particular decision, and we want to
know whether the good that results from some option — compared to an alternative
option — is greater than the harm.
Comparisons of utility differences are difficult, but we do make them, on the
basis of the same sort of information we use to think about tradeoffs within other
individuals. It is clear, for example, that the utility that my friend Bill gains from
having a $30 bottle of wine with his dinner out, instead of a $15 bottle, is less than
the utility gain to someone else from having her malaria cured. (The comparison is
even easier if the disease is fatal without the cure.) If I could purchase a cure for $15
by making Bill forgo the more expensive wine, other things being equal, I ought to
do it. Other comparisons are more difficult, but the difficulty of making them is only
amatterofdegree.
The fact that we make such comparisons does not necessarily make them meaningful.
Comparisons of utilities across people could be like comparisons of the saltiness
of colors. We can make such judgments, and we might even agree somewhat on
them. But there is no truth about them.
Can we imagine some kind of yardstick that would have the same utility for two
people? That would be a starting point. Let us imagine two identical twins with
identical experiences. 3 Suppose each twin is given a thirty-volt electric shock lasting
for one minute. It is reasonable to assume that this has the same utility for both of
them. Pure experiences of this sort could serve as the yardstick we are seeking. We
have no reason to question the equivalence of the experience for both twins.
We could extend this to cases of people less closely related. We know something
about what makes people respond differently to painful experiences, and we could
use this knowledge to make reasonable guesses about the utility of the same event
for different people. The less similar the people are, the more error our judgment
will have, but error is present in all judgments. The point is that we have reasons for
our judgments of interpersonal comparison of utility. They are not like judging the
saltiness of colors.
Once we have the yardstick, we can use it to measure other goals, goals that do
not involve experiences only. We could do this by asking for judgments within in-
3 This is not truly possible, but it is approximately possible, and certainly imaginable, and this is all we
need for a an argument about normative theory.