A junkie without access to his stash is in a state of crisis. The "energy crisis" that exists intermittently when the flow of fuel from unstable countries is cut off or threatened, is a crisis in the same sense. In this essay, Illich examines the question of whether or not humans need any more energy than is their natural birthright. Along the way he gives a startling analysis of the marginal disutility of tools. After a certain point, that is, more energy gives negative returns. For example, moving around causes loss of time proportional to the amount of energy which is poured into the transport system, so that the speed of the fastest traveller correlates inversely to the equality as well as freedom of the median traveller.