If we divide the world crudely into rich nations and poor nations, two thirds of them are desperately poor, and only one third comparatively rich, with the united states the wealthiest of all. metaphorically each rich nation can be seen as a lifeboat full of comparatively rich people. in the ocean outside each lifeboat swim the poor of the world, who would like to get in, or at least to share some of the wealth. what should the lifeboat passengers do? first, we must recognize the limited capacity of any lifeboat. for example, a nation's land has a limited capacity to support a population and as the current energy crisis has shown us, in some ways we have already exceeded the carrying capacity of our land. what metaphor in the passage does hardin use to illustrate his argument?