Abstract
One goal of environmental ethics is to recommend changes to patterns of human life so as to bring inhabited landscapes into line with a vision of the good. However, the complex intertwining of nature and culture in inhabited landscapes makes this project much more difficult, complicating ethical judgment and limiting the efficacy of ethical action. Technological momentum, a model introduced by historian Thomas P. Hughes to describe the development of complex technological systems, can shed some light on these difficulties. The process of metropolitan growth in the United States will serve to illustrate the consequences of technological momentum for environmental ethics and policy.