Population and ethics

1. ‘The population bomb’

The number of people now living is larger than the number who have ever lived in all past generations of humanity taken together. This striking fact of absolute numbers stands alongside a rate of growth which now doubles the population of the world every thirty-five years. Sharp awareness of the threat that these facts and trends present goes back to the early nineteenth century, primarily to the work of Thomas Malthus, who argued that the number of people multiplies in geometric progression while the resources which support their life can be expected to grow at most in arithmetic progression. The threat of overpopulation arising from this gap in rates of growth can be checked either by factors like death from starvation, illness and war, or by preventive measures such as controlling the number of births. Following Malthus, it is commonly believed that there is an ethical asymmetry between the two kinds of checks: the premature death of living people is morally worse than the non-creation of new people. Thus, a rise in life expectancy is generally considered a blessing, while an increase in births is treated as a menace. However, balancing world population is particularly problematic, since overpopulation is primarily due to the decrease in death rates rather than the increase in birth rates. Consequently, even if very restrictive population policies were implemented (such as zero population growth), many decades would pass before the number of births and the number of deaths balanced one other.

Concern with the danger of overpopulation is historically and analytically associated with two major normative issues, themselves interdependent: the just distribution of welfare across generations (usually referred to as the problem of savings); and responsibility for the environment (conservation). Thus, since the 1920s economists have attempted to fix optimum population size in economic terms, such as the highest income per capita across generations, and theories of justice (particularly since Rawls) have tackled the population question through the principles of justice applied intergenerationally (see Future generations, obligations to; Justice). Meanwhile, environmentalists have argued over the last few decades that the number of people in the world should be limited in terms of the carrying capacity of the planet and respect for the integrity of the natural environment, either for the sake of future people (‘shallow ecology’) or for its own sake (‘deep ecology’) (see Environmental ethics). However, one can take the opposite approach and rather than subordinate the issue of population to economic or ecological considerations, treat the existence and number of people as the foundation for both economic justice and environmental policies. Thus, for instance, one may take the existence of a growing population as a given fact which should dictate a new approach to the natural environment in which the wilderness will have a radically weakened status.

The metaphors of ‘the population bomb’ and ‘population explosion’ typically convey a morally negative evaluation of the increase in the number of human beings. However, beyond the empirical debate between the ‘alarmist’, neo-Malthusian view and its opponents who see no danger in population growth as such, a critical philosophical analysis of the issue raises the following questions. Is the size of world population an ethical issue at all? If it is, what are the normative criteria for determining the ‘right’ (or optimal) size? If such criteria can be formulated and justified, what are the ethical constraints in implementing suitable policies for the attainment of this size?