Hardin begins with metaphors. He points out that while the metaphor of earth as a grand spaceship has a certain popularity (or did 23 years ago) it is a flawed metaphor nonetheless. A spaceship has a captain, and couldn't survive without one. The earth has nothng vaguely resembling a captain, the United Natins in particular being a "toothless tiger."
Whatever we may make of the metaphor, we shold note what it was meant to support. By Hardin's own account, it was a way of bolstering the following proposition:
...no single person or instituion has the right to destroy, waste or use more than a fair share of its resources.
The correctness of this view would hardly seem to depend on whether the earth has a captain. But Hardin's reply would no doubt be that if we ae in a situation in which allowing everyone a "fair share" will lead to disaster, then this seemingly innocuous moral principle is dangerous.
In any case, Hardin prefers a different metaphor. Rich nations can be seen as lifeboats. The seas around them are filled with poor people who would like to get in the lifeboat or at least get a shae of the walth. Should we let them in?
Hardin fills out the metaphor. Suppose that our lifeboat has a capacity of 60 people and that there are now 50 people on board. Suppose there are 100 people in the water. If we take them all on board, we get "complete justice, complete disaster," in...