Sustainability rests on maintaining the health of the world environment. Its health, like our own, depends on not over-stressing the system, which means not taking too much away or putting back too much that is toxic or unhealthy. It is the total quantity of stuff coming out of or going back into the world that creates unsustainability. Green goods may arguably be less harmful to the world than those that they replace, but whatever gains they produce will eventually be outweighed by the growth of consumption. Until our growth-based economies are replaced by another form of the political economy, green goods can only slow down the inevitable encounter with the limits of our finite planet. More at John Ehrenfeld.