Act utilitarianism is a utilitarian theory of ethics which asserts that a person's act is morally correct if, and only if, it produces the best possible results (more happiness for more people) in that specific situation. The classical utilitarians, including Jeremy Bentham, John Stuart Mill and Henry Sidgwick, define happiness as pleasure and absence of pain.
Also called "extreme" or direct utilitarianism.
Original, and "official" form of utilitarianism which says that our duty on any occasion is to act in the way which will produce actual overall consequences better than (or at least as good as) those that any other act open to us would produce.
To understand how act utilitarianism works, compare the consequences of watching TV all day tomorrow with the consequences of doing charity tomorrow. One could produce more happiness in the world by doing charity work tomorrow than by watching television all day. According to act utilitarianism, then, the right thing to do tomorrow is to go out and do charitable works; it is not right to stay home and watch television all day.
Act utilitarianism is based on the principle of utility, which is the basis of all utilitarian theories and is best summarized in Bentham's well-known phrase:
"The greatest happiness for the greatest number".
Jeremy Bentham supported his theory with another famous quote of his:
"Nature has placed mankind under two sovereign masters, pain and pleasure. It is for them alone to point out what we should do, as well as to determine what we should do".
Bentham's utilitarianism is a hedonistic theory and begins with the premise that people are hedonistic by nature. This means that he believed that people would actively seek pleasure and avoid pain, if given the opportunity.
Critics sometimes cite such prohibitions on leisure activities as a problem for act utilitarianism. Critics also cite more significant problems, such as the fact that utilitarianism seems to imply that specific acts of torture or slavery would be morally permissible if they produced sufficient happiness.
Difficulties in predicting consequences, including difficulties in principle where self-prediction is concerned, mean that as a practical prescription utilitarianism can only tell us to aim for the best probable outcome, and act utilitarianism has often been superseded by rule utilitarianism.
Source: J J C Smart, 'Extreme and Restricted Utilitarianism', Theories of Ethics, P Foot, ed. (1967); defends the former.
The act utilitarianism is often contrasted with a different theory called rule utilitarianism. Rule utilitarianism asserts that morally correct action is that which is in accordance with a moral rule whose general observance would create the greatest happiness.
What is the difference between act and rule utilitarianism?
Act utilitarianism analyses the consequence of a decision as a particular act, while rule utilitarianism evaluates a consequence as if it were to be replicated later in the future. Act utilitarianism has an initial approach to examining the consequences of a current act. Rule utilitarianism differs by evaluating consequences on the basis of a specific rule followed.
It is sometimes thought that rule utilitarianism avoids the problems associated with act utilitarianism.