"Yet built-in conflict looms. Growth, both material and economic, simply cannot continue indefinitely on a finite planet. Economists—supported by only a short period of empirical evidence—have argued that substitution and decoupling are mechanisms that can allow for indefinite growth. Plenty of examples from the past bolster such arguments. On substitution, the Stone Age did not end due to a lack of stones, one pithy argument goes. On decoupling, trading fine art has a tiny energy-to-monetary ratio. But the overall evidence does not support the idea that the basic operation of the modern economy can happen without massive material and energy throughput. In practice, efficiency gains are largely erased by further growth. Remember that all such past examples from the industrial era have taken place in the context of unsustainable exploitation of finite resources. The future need not look like the recent past—in fact, cumulative irreversible impacts mean that it can’t."