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Rule utilitarianism is a form of utilitarianism that says an action is right as it conforms to a rule that leads to the greatest good, or that "the rightness or wrongness of a particular action is a function of the correctness of the rule of which it is an instance."
For rule utilitarians, the correctness of a rule is determined by the amount of good it brings about when followed. In contrast, act utilitarians judge an act in terms of the consequences of that act alone (such as stopping at a red light), rather than judging whether it faithfully adhered to the rule of which it was an instance (such as, "always stop at red lights"). Rule utilitarians argue that following rules that tend to lead to the greatest good will have better consequences overall than allowing exceptions to be made in individual instances, even if better consequences can be demonstrated in those instances.
In his 1861 book Utilitarianism, John Stuart Mill defends the concept of rights in terms of utility: "To have a right, then, is, I conceive, to have something which society ought to defend me in the possession of. If the objector goes on to ask, why it ought? I can give him no other reason than general utility." Whether Mill was a rule utilitarian is a matter of controversy. This passage from Utilitarianism seems to suggest that he was:
In the case of abstinences indeed — of things which people forbear to do from moral considerations, though the consequences in the particular case might be beneficial — it would be unworthy of an intelligent agent not to be consciously aware that the action is of a class which, if practiced generally, would be generally injurious, and that this is the ground of the obligation to abstain from it.
But Mill also argues that it is sometimes right to violate general ethical rules:
… justice is a name for certain moral requirements, which, regarded collectively, stand higher in the scale of social utility, and are therefore of more paramount obligation, than any others; though particular cases may occur in which some other social duty is so important, as to overrule any one of the general maxims of justice. Thus, to save a life, it may not only be allowable, but a duty, to steal, or take by force, the necessary food or medicine, or to kidnap, and compel to officiate, the only qualified medical practitioner.
Other things being equal people are happier if their society follows rules so people know what types of behaviour they can expect from others in given situations. Therefore utilitarians can justify a system that goes, "Keep to the rules unless there is a strong reason for breaking them."
Strong Rule Utilitarianism
Strong rule utilitarianism is the utilitarian theory that says the moral rules should be adhered to at all times. This theory does not deteriorate into Act utilitarianism like weak rule utilitarianism, but is an absolutist theory and has all the same issues as other theories that support following a set of rules all the time. This problem can be illustrated with the example of a murderer who wants to kill your friend, who is hiding in your house. The murderer asks you where your friend is, so that they can kill your friend. The moral rule says that lying is wrong so the strong rule utilitarian says you should tell them where your friend is, which most people would say is the wrong thing to do as it will result in your friend's death. The response usually presented to this criticism is that the above scenario is very improbable and that, if applied universally, the moral rule would create a lot more happiness than sadness because in the majority of situations, telling the truth leads to more trust and happier people.
A specific criticism of rule utilitarianism states that it collapses into act utilitarianism. David Lyons argued that collapse occurs because for any given rule, in the case where breaking the rule produces more utility, the rule can be sophisticated by the addition of a sub-rule that handles cases like the exception. This process holds for all cases of exceptions, and so the 'rules' will have as many 'sub-rules' as there are exceptional cases, which, in the end, makes an agent seek out whatever outcome produces the maximum utility.
- Garner, Richard T.; Bernard Rosen (1967). Moral Philosophy: A Systematic Introduction to Normative Ethics and Meta-ethics. New York: Macmillan. p. 70. ISBN 0-02-340580-5.
- Mill, John Stuart (1861). Utilitarianism.
- "Rule Consequentialism". Stanford Encyclopedia of Philosophy. 2003-12-31. Retrieved 2007-03-11.
- Forms and Limits of Utilitarianism, 1965.
- Allen Habib (2008), "Promises", in the Stanford Encyclopedia of Philosophy.
- Brad Hooker's entry on rule consequentialism in the Stanford Encyclopedia of Philosophy: 
- Brad Hooker, Ideal Code, Real World Oxford University Press, 2000, new edition 2002
- Foundations of Morality at the Mises Institute Hazlitt, Henry (1964). The Foundations of Morality. Irvington-on-Hudson,NY: Foundation for Economic Education.
- Smart, J. J. C (October 1955). Extreme and Restricted Utilitarianism (Speech). The Victorian Branch of the Australasian Association of Psychology and Philosophy.