Indicates some of the different concepts of sustainable economic development and raises queries about how much present generations are concerned with future generations. A variety of conditions (ranging from very weak to very strong) have been suggested for achieving sustainable development. These are outlined. The prospect that the accumulation of man-made capital may result in unsustainable economic development is discussed and the welfare consequences of the conversion of natural capital are considered in a historical context. This leads on to a discussion of different types of capital: man-made and natural. Division of the total stock of capital into these categories is now common. However, there appears to be a gap because heritage capital (for example, varieties of crops and animals developed by human interference in nature) do not fit well into this framework. Some reasons why economic production may not be maintained or maximised are considered. They include the presence of externalities, open access to resources and the presence of public goods and bads. It is pointed out that it is undesirable to sustain everything, including all industries. While it might seem appealing to seek sustainable strategies that satisfy multiple criteria (such as economic viability, political and social acceptability and ecological sustainability), it is possible that such strategies rarely exist, if at all.