"Our most serious problem, perhaps, is that we have become a nation of fantasists. We believe, apparently, in the infinite availability of finite resources."

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This whole issue of limits to growth, which provides a psychological, as well as a physical, cap on potential expansion of activity and awareness, has had a very depressing effect on many people.... I don't for a moment think that there's any concept which anyone's working with now which will be followed as a straightforward scenario. But the idea embodied in concepts such as space colonization or space industrialization, or availability of nonterrestrial resources, is fundamental, and it will change the way in which people look at the future.

— Rusty Schweickart