Entropy
Nature has a particular way to deal with things. An element of chance is inherent in natural processes. A disorderly arrangement is much more probable than an orderly one if laws of nature are allowed to act without interference. Entropy is to consider that all processes of change are irreversible. This include natural processes as the growing of a plant, as well as technological processes, such as the burning of fossil fuels in combustion engines. The economy uses low entropy energy and matter from its surrounding natural environment (such as oil and coal), to produce consumption goods, and discards high entropy wastes and dissipated heat back into the environment (such as carbon dioxide). How much degradation of resources can or should be tolerated as a result of economic activity? What the sustainable scale of the economy can or should be in relation to the ecosystems which contain and sustain it?