With sufficiently cheap energy, pollution would become a thing of the past; at current levels of energy usage, this is impractical. Most of our species is still locked in the subsistence-agriculture trap, and simply extending the First World system of coal- and petroleum-fueled industrialism to them would probably destroy the planet.
This knowledge is the specter at the feast of progress, now that Western civilization is overcoming the self-inflicted wound of 1914 and its consequences. The so-called "soft" path is nothing more than a return to the animalistic misery of pre-industrial times; sunlight is simply too diffuse to maintain even the present level of consumption. Hard, concentrated energy is the essential prerequisite for an economy like ours; conservation and increased efficiency merely delay the problem without solving it. Restricting growth means a boot in the face of the world's have-nots; a tiny island of comfort on a swelling mound of resentful pain; eventually it means impovershing everyone.
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