the establishment of a new mode of production. In opposition to his liberalist predecessors in the field, Marx did not regard natural resource scarcity as a factor constraining future economic growth; instead, the capitalist mode of production was to be overturned before the productive forces of society could fully develop, bringing about an abundance of goods in a new society based on the principle of "from each according to ability, to each according to need" — that is, communism. The assumption, based on technological optimism, was that communism would overcome any resource scarcity ever to be encountered. For ideological reasons, then, orthodox Marxism has mostly been opposed to any concern with natural resource scarcity ever since Marx's own day. However, the march of history has been hard on this ideology: By 1991, German sociologist Reiner Grundmann was able to make the rather sweeping observation that "Orthodox Marxism has vanished from the scene, leftism has turned green, and Marxists have become ecologists." In neoclassical economics, on the other hand, the preoccupation with society's long term growth and development inherent in classical economics was abandoned altogether; instead, economic analysis came to focus on the study of the relationship between given ends and given scarce means, forming the concept of general equilibrium theory within an essentially static framework. Hence, neoclassical economics achieved greater generality, but only by asking easier questions; and any concern with natural resource scarcity was neglected. For this reason, modern ecological economists have deplored the simplified and ecologically harmful features of neoclassical economics: It has been argued that neoclassical economics has become a pseudoscience of choice between anything in general and nothing in particular, while neglecting the preferences of future generations; that the very terminology of neoclassical economics is so ecologically illiterate as to rarely even refer to natural resources or ecological limits; and that neoclassical economics has developed to become a dominant free market ideology legitimizing an ideal of society resembling a perpetual motion machine of economic growth at intolerable environmental and human costs. Taken together, it has been argued that "... if Judeo-Christian monotheism took nature out of religion, Anglo-American economists (after about 1880) took nature out of economics." Almost one century later, Herman Daly has reintegrated nature into economics in his concept of a steady-state economy (see below). John Maynard Keynes's concept of reaching saturation John Maynard Keynes was the paradigm founder of modern macroeconomics, and is