Starting from the early 1990s support for ‘sustainable development’ (henceforth: SD) has become very widespread. At the Rio summit in 1992 the vast majority of nation-states have formally committed themselves to SD in signing Agenda 21 (UNCED 1992) — a commitment renewed at the 2002 World Summit on Sustainable Development in Johannesburg and the 2012 Earth Summit, also known as Rio+20. Whilst the rhetoric has shifted somewhat as fads come and go — ‘green growth’ has recently become a more popular phrase than SD — it remains true that since the early 1990s there has been hardly any politician, academic or businessperson who does not call for making development sustainable. In some sense this is not surprising: SD is like freedom or peace — that is, something to which no reasonable person would overtly object. Development always sounds good and that it has to be sustainable seems self-evident. In this book two economic paradigms of SD — ‘weak sustainability’ and ‘strong sustainability’ — will be analysed with the objective of exploring their limits. ‘Weak sustainability’ (henceforth: WS) is based upon the pioneering work of two neoclassical economists: Robert Solow (1974a, 1974c, 1986, 1993a, 1993b), a Nobel Laureate, and John Hartwick (1977, 1978a, 1978b, 1990, 1993), a famous resource economist.