From "THE TRAGEDY OF THE COMMONS" by GARRETT HARDIN
We can make little progress in working toward optimum population size until we explicitly exorcize the spirit of Adam Smith in the field of practical demography. In economic affairs, The Wealth of Nations (1776) popularized the ‘invisible hand’, the idea that an individual who ‘intends only his own gain’, is, as it were, ‘led by an invisible hand to promote . . . the public interest’. Adam Smith did not assert that this was invariably true, and perhaps neither did any of his followers. But he contributed to a dominant tendency of thought that has ever since in- terfered with positive action based on rational analysis, namely, the tendency to assume that decisions reached individually will, in fact, be the best decisions for an entire society. If this assumption is correct it justifies the continuance of our present policy of laissez-faire in repro- duction. If it is correct we can assume that men will control their indi- vidual fecundity so as to produce the optimum population. If the assumption is not correct, we need to re-examine our individual freedoms to see which ones are defensible.
Tragedy of Freedom in a Commons
The rebuttal to the invisible hand in population control is to be found in a scenario first sketched in a little-known pamphlet in 1833 by a math- ematical amateur named William Forster Lloyd (1794-1852). We may well call it ‘the tragedy of the commons’, using the word ‘tragedy’ as the philosopher Whitehead used it: ‘The essence of dramatic tragedy is not unhappiness. It resides in the solemnity of the remorseless working of things.’ He then goes on to say, ‘This inevitableness of destiny can only be illustrated in terms of human life by incidents which in fact involve unhappiness. For it is only by them that the futility of escape can be made evident in the drama.’
The tragedy of the commons develops in this way. Picture a pasture open to all. It is to be expected that each herdsman will try to keep as many cattle as possible on the commons. Such an arrangement may work reasonably satisfactorily for centuries because tribal wars, poaching, and disease keep the numbers of both man and beast well below the carrying capacity of the land. Finally, however, comes the day of reckoning, that is, the day when the long-desired goal of social stability becomes a reality. At this point, the inherent logic of the commons remorselessly generates tragedy.
As a rational being, each herdsman seeks to maximize his gain. Ex- plicitly or implicitly, more or less consciously, he asks, ‘What is the util- ity to me of adding one more animal to my herd?’ This utility has one negative and one positive component.
1) The positive component is a function of the increment of one ani- mal. Since the herdsman receives all the proceeds from the sale of the additional animal, the positive utility is nearly + 1.
2) The negative component is a function of the additional overgrazing created by one more animal. Since, however, the effects of overgraz- ing are shared by all the herdsmen, the negative utility for any par- ticular decision-making herdsman is only a fraction of 1.
Adding together the component partial utilities, the rational herdsman concludes that the only sensible course for him to pursue is to add an- other animal to his herd. And another; and another....But this is the conclusion reached by each and every rational herdsman sharing a com- mons. Therein is the tragedy. Each man is locked into a system that compels him to increase his herd without limit-in a world that is lim- ited. Ruin is the destination toward which all men rush, each pursuing his own best interest in a society that believes in the freedom of the commons. Freedom in a commons brings ruin to all.