A finite world can support only a finite population; therefore, population growth must eventually equal zero.

A coldly rationalist individualist can deny that he has any obligation to make sacrifices for the future.

The rational man finds that his share of the cost of the wastes he discharges into the commons is less than the cost of purifying his wastes before releasing them.

Thou shalt not transgress the carrying capacity

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.

Ecological differentiation is the necessary condition for coexistence.

The rational herdsman concludes that the only sensible course for him to pursue is to add another animal to his herd. And another; and another . . . But this is the conclusion reached by each and every rational herdsman sharing a commons. 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 limited. 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.