Sustainable cities: Oxymoron, utopia, or inevitability?

Some people argue that, by definition and common sense, cities can not be sustainable. Others say that the idea is utopian, but that we can learn from literacy examples. Still others assert that cities will, must, and are becoming sustainable. This article explores each point of view, cites examples of steps toward sustainability currently being taken by various types of communities, notes common elements among them, and offers a resolution based on different definitions of sustainability.