Writing in 1968 to a highly educated scientific audience, Garrett Hardin presented a compelling formulation of the population problem. He posed the population problem in stark terms. First, he examined the relation of population to resources, and concluded population must be brought under control. He then analyzed the dynamics that have caused population to swell. From this analysis, he proposed solutions. Certain aspects of his problem formulation still deserve careful consideration, but today, richer ideas for solutions complement those he proposed.
Hardin rejected the wild hope that improved food production technology will allow an indefinite increase in population: "a finite world can support only a finite population." More specifically, we cannot hope to provide growth in both the material quality of life and population. Mathematically, both factors cannot be maximized at once; and biophysically, the calories available per person must decrease as population increases. Thus he invalidated Jeremy Bentham's goal of "the greatest good for the greatest number," and concluded "the optimum population is, then, less than the maximum." (Notably, also according to this logic, the strategy of decreasing population by increasing the "standard of living" (consumption), as predicted by the demographic transition model, might be reexamined.)
But we have difficulty choosing to limit population, and choosing between which goods to pursue in a world that cannot provide for every different good because we have left the choice of "the good" entirely to individuals in our capitalistic society. We act as if individual choices will somehow solve collective problems such as population. Adam Smith's laissez-faire doctrine of the invisible hand tempts us to think that a system of individuals pursuing their private interests will automatically serve the collective interest. But applying this would be disastrous. Hardin employed a key metaphor, the Tragedy of the Commons (ToC) to show why. When a resource is held "in common," with many people having "ownership" and access to it, Hardin reasoned, a self-interested "rational" actor will decide to increase his or her exploitation of the resource since he or she receives the full benefit of the increase, but the costs are spread among all users. The remorseless and tragic result of each person thinking this way, however, is ruin of the commons, and thus of everyone using it. The straightforward application of the "herdsman" analogy to world population is that each couple expects to experience a large benefit from having another child, but only a little of the full social and ecological cost.
Both Hardin's solutions, and their weaknesses, stem from things assumed in this model. His basic solution is that we must abandon the commons system in breeding (as we have already in food production and pollution - instances where we have used privatization and laws to achieve this). People must no longer be free to add unlimited numbers of offspring to the total load on the earth's ecosystems. This sounds simple enough, but the key question is how this restriction is to be achieved.
Hardin's rejection of some solutions stems from the individualistic assumptions of his metaphor. Particularly, he rejects appeals to conscience, because they would "select for" those without scruples over having more children. It is doubtful however that conscience is entirely genetic, nor perfectly transmitted by learning in families. Further, his assumption that were it not for "welfare," over-breeders would have to pay for their profligacy, runs in the face of evidence that parents whose infants die are paradoxically both more inclined to get pregnant again, and less likely to emotionally invest in their young. Welfare may indeed be part of solving the population problem. This is just one example where Hardin fails to differentiate reproductive behavior according to socio-economic conditions.
HARDIN'S KEY ASSUMPTIONS AND PROBLEM FORMULATION:
1. The world is biophysically finite.
2. Over-population is an example of the tragedy of the commons (ToC).
3. The "commons" system for breeding must be abandoned (as it has been for other resources).
4. The problem is then to gain peoples' consent to a system of coercion.
While extremely clean & efficient technology might allow more people and material consumption than Hardin imagined, ultimately the trade-off between human numbers and quality of life would remain.
The model of the ToC, while compelling, generalizes from a faulty historical case study. In fact communities managed their commons; real humans are not so exclusively self-interested as to not care what their fellows think of them, and not be able to manage common concerns. It is possible that communities do observe and regulate members' fertility, rather than leaving it up to individual choice. This might be coercion on a small scale, but it could accommodate much individual need also.
The assumption that were it not for "welfare," over-breeders would have to pay for their profligacy runs in the face of evidence that parents whose infants die are paradoxically both more inclined to get pregnant again, and less likely to emotionally invest in their young. Child survival and welfare enable parents to stop at fewer children, and provide security in old age, independent from offspring's or husband's income.
People's motivations to have babies are not the same everywhere and at every time. They vary depending on economic circumstances, culture, and gender. Understanding and altering these conditions is another route to changing fertility decisions. The cost/benefit conditions of childbearing decisions can be altered in many ways. But some such strategies may require an unrealistic degree of material economic development. Ones which do not include wealth redistribution, meeting unmet need, improving the economic and educational options for girls and women, and increasing accountability of fathers.
Blunt forms or coersion such as China's one-child policy are likely to have negative unintended consequences.