The unsustainability of capitalism was recognised from the very beginnings of ‘political economy’ in the nineteenth century. The Marginal Revolution a few decades later (which, tellingly, saw the quiet retirement of ‘political’ from the description of an economist’s object of study) brought with it further theorising on the limitations of continual growth. For the likes of Adam Smith, David Ricardo, Thomas Malthus and John Stuart Mill, every ‘commercial society’ inevitably reaches its ‘natural limits’ once population growth exceeds productivity growth.