Sustainability is a term that has been given many different meanings, all of which derive from the perception that the existing model of industrial society is on a fatal trajectory. Three responses to this perception are possible. The dominant view holds that the trajectory will be altered by innovations that conserve the basic pattern of life that has evolved since World War II in the advanced societies. Those sceptical of this view sometimes propose a return to much simpler ways, the abandonment of industrial society and all its works. Finally, a third possibility is the innovation of new technologies and social arrangements that fundamentally alter the pattern but which reproduce the most basic values of industrial society.