Most people regard sustainable development as essentially a matter of intertemporal ethics. This paper argues that the crux is excessive environmental disruption due to an inadequate account for the external costs on other people now, rather than due to inadequate concern for our grandchildren. Even with full concern, the excessive disruption will be virtually unchanged. This paper also argues that intertemporal impartial welfare maximization is the appropriate objective to pursue. This involves treating the welfare of future generations on a par with that of our own but with all welfare values appropriately weighted by the probability of their realization. Since the probability of non-survival is cumulative, this acts like a discount rate, though justified on completely different grounds. This solves the paradoxes of non-existence of a solution or incomplete rankings associated with choices involving an infinite time horizon without discounting. Sustainable development has been a hot topic for decades now. Most people regard it as essentially a matter of intertemporal ethics. This paper argues that the crux of the matter is excessive environmental disruption. With the proper control of environmental disruption, sustainable development will not be a problem in practice. Moreover, with or without proper control, impartial welfare maximization is sufficient to answer problems of sustainable development and intertemporal ethics at least at the conceptual level. Copyright © 2004 John Wiley & Sons, Ltd and ERP Environment.