JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 169.230.243.252 on TueABSTRACT. We appraise neoclassical theory of growth with natural capital for the estimation of indicators for sustainability. Relationships between four theoretically distinct measures are clarified: Hicksian "change in capital stock value"; the Hartwick "net savings" (which excludes capital gains); "sustainable national income" (SNI); and "environmentally-adjusted net national product" (gNNP). An overlapping generations (OLG) general equilibrium model with depletable natural capital demonstrates the significance of model parameters determining technical feasibility and intertemporal distribution of consumption. Irremediable uncertainties in model specification and empirical measurement mean that the neoclassical theory is not robust for defining or estimating indicators for sustainability. (JEL 011) All use subject to JSTOR Terms and Conditions 73(4) Faucheux et al.: Natural Capital Theory 529 gNNP as an indicator of prospects for sustainable future welfare levels relative to the current level of consumption.1 The usual response in the economics literature relies on theoretical results from neoclassical growth-with-natural-capital theory.Part II of the paper reviews key elements of the neoclassical theory of economic growth with natural capital. Part III then presents a simple overlapping generations general equilibrium model with a depletable natural resource, which is used to highlight the significance for "socially optimum" consumption timepaths of axiomatic assumptions relating to model structure and parametrization, in particular presumptions about substitutability, time-discounting, and relative prices as measures of opportunity costs. On this foundation we assess the ambition and limitations of recent work, both theoretical and applied, that has sought to assess by the "weak" criteria the "sustainability" or nonsustainability of national economies. Part IV gives a synthetic overview of the search for macroeconomic indicators of sustainable development based on the neoclassical natural capital theoretical approaches. Part V assesses the combined impact of the theoretical and empirical limits to validity of the "weak" sustainability indicators. We will conclude, in Part VI, with the assessment that insurmountable problems of aggregation and measurement at both theoretical and empirical levels mean that the neoclassical theory is not robust-and cannot ever be made robust-as abasis for deriving reliable indicators for sustainability.