Population and ethics

2. Optimum population size

The question of optimal population size touches upon the deepest problems concerning the nature of value: is value ascribed impersonally to ‘the world’, or only to actual human beings whose very existence is presupposed by any evaluation? The first view (impersonalism) treats the population issue as a function of a value or an end considered in abstraction. The ideal number of people is that which would promote that end to the maximal degree. This could be average or total utility, the foundation of a Kantian ‘kingdom of ends’, or the establishment of a Marxian classless society. The second view (commonly called ‘person-affecting’) holds that moral evaluation applies only to existing human beings and hence cannot serve to assess the value of any particular number of human beings, indeed not even of the very existence of humanity. According to this view, ‘good’ is always ‘good for’, and consequently one cannot say that to be born (or not to be born) is a morally good (or bad) thing. Increasing or reducing the number of future people cannot in the person-affecting view be considered morally desirable (or obligatory) since the interests of no particular people are promoted or rights of particular persons respected either by bringing them into the world or by preventing them from coming into existence.

The two views face difficult problems, which have been extensively discussed by Derek Parfit (1984). Take first utilitarianism, which has been the most popular version of impersonalism in the context of population questions (see Utilitarianism). Total utilitarianism leads to the so-called ‘repugnant conclusion’, according to which the world would be overcrowded with people whose extremely low quality of life is offset by their huge number, thus achieving the highest value of total utility. Average utility fares no better, since it recommends a policy which on the one hand would make it obligatory to bring a new child into the world whose happiness would be a little above the current average, and on the other hand would prohibit the addition of extra people whose standard of living would be even slightly below that enjoyed by present people. Negative utilitarianism, which aims at the overall reduction of pain rather than the promotion of happiness, could lead to the absurd ideal of total abstention from procreation.

Turning from these impersonal criteria to the person-affecting view, we are confronted by the problem of identity. We cannot say that population policies serve the interests or the welfare of future people since they themselves directly and indirectly affect the identity of those people. Thus, if we decide on a restrictive population policy, for example, by introducing family planning programmes, the people who are actually going to be born are not the same as those who would have been born had we abstained from interfering in people’s reproductive choices. The idea of an optimal population size is therefore logically incoherent. On the one hand, there is the indeterminacy of an ideal based on the combination of two variables; namely, ‘maximum happiness to maximum people’, which has been shown traditionally to have no unique ‘solution’, as it can be achieved equally by raising the amount of happiness or by raising the number of people. On the other hand, there is the incommensurability of the respective value of two populations consisting of different individuals; namely, the problem of identity, in which case the person-affecting view makes it impossible to compare the value of the lives of alternative sets of people.

Other philosophers have noted the special difficulties incurred in applying contract theory to the issue of population. These derive from the problem of representation in Rawls’ ‘original position’: who takes part in the initial contract? All possible people (but can these be even theoretically identified)? All actual people (but their number is exactly the issue to be decided by the contract)? Representatives of each generation, or rather a representative of one particular generation, who does not know which generation it is? Contractors negotiating their coming into being, their very existence, is an idea which leads to interesting paradoxes that have been discussed primarily by John Rawls (1971) and his critics (see Contractarianism §7).

Our intuitions concerning optimal population size are also indeterminate. Beyond some clear upper and lower limits of over- and underpopulation, we do not have any firm beliefs as to the right balance between the quantity and quality of human lives. Furthermore, our preferences concerning numbers are typically ‘adaptive’, that is to say they are themselves formed and affected by the size of population to which we belong. We thus tend to project our own preferences on our descendants, assuming (without justification) that they would not want to live in a more crowded environment than we did. From this welfarist perspective, optimal population size is a myth and the population issue lies in principle beyond the scope of ethics. Yet, we can be sure that future generations are going to have some basic needs and wants which will be hard to fulfil if the rate of population growth remains unchecked. This in most views provides a moral justification for control measures.