Consequentialism is a theory that says whether something is good or bad depends on its outcomes.

An action that brings about more benefit than harm is good, while an action that causes more harm than benefit is not. The most famous version of this theory is utilitarianism.

Although there are references to this idea in the works of ancient philosopher Epicurus, it’s closely associated with English philosopher Jeremy Bentham.

Bentham’s theory of utilitarianism focussed on which actions were most likely to make people happy. If happiness was the experience of pleasure without pain, the most ethical actions were ones that caused the most possible happiness and the least possible pain.

He even developed a calculator to work out which actions were better or worse – the ‘felicific calculus’. Because it counted every person’s pleasure or pain as the same, regardless of age, wealth, race, etc. utilitarianism could be seen as a radically egalitarian philosophy.

Bentham’s views are most closely aligned with act utilitarianism.  This basic form of consequentialism holds an action as ethical if and only if it produces more beneficial/pleasure-causing outcomes than negative/pain-causing ones. Whenever we are faced with a decision, an act consequentialist will expect us to ask that question.

John Stuart Mill, a student of Bentham’s, disagreed. He believed it was too difficult for a society to run if it had to consider the specific costs/benefits of every single action. How could we have speeding laws, for example, if it would sometimes be ethical to break the speed limit?

Instead, Mill believed we should figure out which set of rules would create the most happiness over an extended period of time and then apply those in every situation. This was his theory of rule utilitarianism.

According to this theory, it would be unethical for you to speed on an empty street at two o’clock in the morning. Even if nobody would be hurt, our speeding laws mean less people are harmed overall. Keeping to those rules ensures that.

Consequentialism is an attractive ethical approach because it provides clear and practical guidance – at least in situations where outcomes are easy to predict. The theory is also impartial. By asking us to maximise benefit for the largest number of people (or, for Peter Singer and other preference utilitarians, creatures who have preferences), we set aside our personal biases and self-interest to benefit others.

One problem with the theory is that it can be hard to measure different benefits to decide which one is morally preferable. Is it better to give my money to charity or spend it studying medicine so I can save lives? Many forms of consequentialism have been proposed that attempt to deal with the issue of comparing moral value.

The other concern people express is the tendency of consequentialism to use ‘ends justify the means’ logic. If all we are concerned with is getting good outcomes, this can seem to justify harming some people in order to benefit others. Is it ethical to allow some people to suffer so more people can live well?