"At present population levels, we are putting unprecedented pressure on finite resources. We are conducting a grand-scale, unauthorized experiment on the 4.5 billion-year-old planet. The fact that we have not hit the bounds in a few generations of outrageous growth should not be taken as evidence for our long-haul prospects. We live like kings today, on the backs of [at least] roughly 100 energy slaves each (human metabolism is 100 Watts, but Americans enjoy 10 KW of continuous power). Our richness is very much tied to surplus energy availability, and that so far has been a story of finite [hydrocarbon-based] fossil fuels. But even under solar power, we can’t continue our track record of 3% energy growth per year for even several hundred years! Global physical limits—thermodynamic, energy return on energy invested, finite arable land, water, fisheries, climate change, etc.—are all asserting themselves to remind us that nature doesn’t care about our dreams."