The utility monster is a thought experiment

Thought experiment

A thought experiment or Gedankenexperiment considers some hypothesis, theory, or principle for the purpose of thinking through its consequences...

 in the study of ethics

Ethics

Ethics, also known as moral philosophy, is a branch of philosophy that addresses questions about morality—that is, concepts such as good and evil, right and wrong, virtue and vice, justice and crime, etc.Major branches of ethics include:...

. It was created by philosopher Robert Nozick

Robert Nozick

Robert Nozick was an American political philosopher, most prominent in the 1970s and 1980s. He was a professor at Harvard University. He is best known for his book Anarchy, State, and Utopia , a right-libertarian answer to John Rawls's A Theory of Justice...

 in 1974 as a criticism of utilitarianism

Utilitarianism

Utilitarianism is an ethical theory holding that the proper course of action is the one that maximizes the overall "happiness", by whatever means necessary. It is thus a form of consequentialism, meaning that the moral worth of an action is determined only by its resulting outcome, and that one can...

.

In the thought experiment, a hypothetical being is proposed who receives as much or more utility

Utility

In economics, utility is a measure of customer satisfaction, referring to the total satisfaction received by a consumer from consuming a good or service....

 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, it would justify the mistreatment and perhaps annihilation of everyone else, according to the doctrine of utilitarianism.

According to the philosopher Robert Nozick

Robert Nozick

Robert Nozick was an American political philosopher, most prominent in the 1970s and 1980s. He was a professor at Harvard University. He is best known for his book Anarchy, State, and Utopia , a right-libertarian answer to John Rawls's A Theory of Justice...

:

"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.

It is the opposite of the mere addition paradox

Mere addition paradox

The mere addition paradox is a problem in ethics, identified by Derek Parfit, and appearing in his book, Reasons and Persons . The paradox identifies apparent inconsistency between three seemingly true beliefs about population ethics by arguing that utilitarianism leads to an apparent overpopulated...

, which argues that utilitarianism may lead to a very heavily populated dystopic world.