By way of a thought experiment, make the following pessimistic assumptions about the near and far future. Assume that within the next century we will gradually lose the struggle to sustain the environment and that moderately scarce natural resources will become extremely scarce, due both to increased levels of expectation by the privileged and to increased population. Assume that within the next fifty years the world's population will double but then begin to level off. The best scientific assessment of our prospects for saving the environment in a way that will sustain even a quarter of that population over time (say, several centuries) turns out to be that it cannot be done.