The Tragedy of the Commons, and What Hardin Actually Described

In one line

An essay of 1968 that gave resource law its most quoted phrase, and whose argument is about a pasture with no rules rather than about a pasture held in common.

In the wording a student can write in an exam: Garrett Hardin, in "The Tragedy of the Commons", Science, 13 December 1968, asked the reader to picture a pasture open to all; each herdsman, as a rational being seeking to maximise his gain, asks what the utility to him is of adding one more animal, and finds that he receives all the proceeds of the additional animal while the cost of the overgrazing it causes is shared among all the herdsmen; so he adds another, and another, and so does every other herdsman, and each is locked into a system that compels him to increase his herd without limit in a world that is limited.

The argument, step by step

The scenario. A pasture open to all. Hardin notes that such an arrangement may work for centuries, because war, poaching and disease keep the numbers of men and beasts well below the carrying capacity of the land. The tragedy begins on the day social stability is achieved, that is, when those checks stop operating.

The calculation. Each herdsman asks what one more animal is worth to him. The positive component is nearly the whole value of the animal, because he receives all the proceeds of its sale. The negative component is the additional overgrazing, but that is shared among all the herdsmen, so his own share of it is a fraction.

The conclusion. The sum is positive, so he adds the animal. So does everybody. Ruin is where all of them are heading, each pursuing his own best interest.

The word "tragedy". Hardin takes it from Whitehead and uses it to mean not unhappiness but, in the phrase he quotes, "the remorseless working of things". That is why the essay says the outcome is inevitable rather than wicked: nobody in it is behaving badly by the lights of his own interest.

What Hardin actually described, and why it matters

He described a pasture "open to all". That is open access, the fourth regime in the last chapter, not common property. There is no defined group, no power to exclude, and no rule about how many animals a herdsman may put on.

Historically that is not what an English common was. A common was stinted: the number of beasts a commoner could turn out was fixed by his holding, and the manorial court enforced it. A commons with a stint is common property; a pasture open to all is not.