Today's economic theory usually neglects the role of nature and environment. To make sustainability work it is, however, essential to (re-)integrate nature into the standard concepts of economics, especially by incorporating natural factors into the production function. It must be acknowledged that economic growth is not (only) the result of technical change but is mainly caused by rising energy-inputs into the economy, and that this is necessarily followed by resource exhaustion and pollution. Therefore, nature must not only be taken into account as a central factor of production but also in the form of environmental quality which is the basis for human quality of life. A numeric example shows that a small, but steady decrease of yearly resource consumption is already apt to redirect the economy on a path of sustainable development. (C) 1998 Elsevier Science B.V. All rights reserved.