Ivan Illich poses that human problems must be solved by the impressment of still more "energy slaves' to meet the expanding demand of human masters. The two solutions consist of securing the current source of the drug, or finding a different, more secure pusher. 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.