linguistic:translation, quality:correction
Average versus total happiness

In The Methods of Ethics, Henry Sidgwick asked, "Is it total or average happiness that we seek to make a maximum?" Paley notes that, although he speaks of the happiness of communities, "the happiness of a people is made up of the happiness of single persons; and the quantity of happiness can only be augmented by increasing the number of the percipients, or the pleasure of their perceptions" and that if extreme cases, such as people held as slaves, are excluded the amount of happiness will usually be in proportion to the number of people. Consequently, "the decay of population is the greatest evil that a state can suffer; and the improvement of it the object which ought, in all countries, to be aimed at in preference to every other political purpose whatsoever." A similar view was expressed by Smart, who argued that, all other things being equal, a universe with two million happy people is better than a universe with only one million happy people.

Since Sidgwick raised the question it has been studied in detail and philosophers have argued that using either total or average happiness can lead to objectionable results.

According to Derek Parfit, using total happiness falls victim to the repugnant conclusion, whereby large numbers of people with very low but non-negative utility values can be seen as a better goal than a population of a less extreme size living in comfort. In other words, according to the theory, it is a moral good to breed more people on the world for as long as total happiness rises.

On the other hand, measuring the utility of a population based on the average utility of that population avoids Parfit's repugnant conclusion but causes other problems. For example, bringing a moderately happy person into a very happy world would be seen as an immoral act; aside from this, the theory implies that it would be a moral good to eliminate all people whose happiness is below average, as this would raise the average happiness.

William Shaw suggests that the problem can be avoided if a distinction is made between potential people, who need not concern us, and actual future people, who should concern us. He says, "utilitarianism values the happiness of people, not the production of units of happiness. Accordingly, one has no positive obligation to have children. However, if you have decided to have a child, then you have an obligation to give birth to the happiest child you can."