Utility Monster

The utility monster is a thought experiment in the study of ethics. It was created by philosopher Robert Nozick in 1974 as a criticism of utilitarianism.

In the thought experiment, a hypothetical being is proposed who receives as much or more utility from each additional unit of a resource he consumes as the first unit he consumes. In other words, the utility monster is not subject to diminishing marginal returns with regard to utility, but instead experiences constant marginal returns, or even increasing marginal returns.

Since ordinary people receive less utility with each additional unit consumed, if the utility monster existed, the doctrine of utilitarianism would justify the mistreatment and perhaps annihilation of everyone else, according to Nozick's argument.

In his words:

Utilitarian theory is embarrassed by the possibility of utility monsters who get enormously greater sums of utility from any sacrifice of others than these others lose . . . the theory seems to require that we all be sacrificed in the monster's maw, in order to increase total utility.

This thought experiment attempts to show that utilitarianism is not actually egalitarian, even though it appears to be at first glance.

Some ways of aggregating utility, such as based on Rawls' maximin or difference principle, can circumvent the conclusion that all units should be given to the utility monster. In particular, maximin sets a group's utility as that of the being with least utility. Thus, giving units to the utility monster fails to change the group's utility unless the utility monster has the least utility. Even if the utility monster has the least utility, maximin would only prefer allocating units to the monster until it catches up with the member that has next-to-least utility.