Back to your question: What is the underworld in my book? In the beginning, I had a straightforward definition: it was a mine, or a pit dug into the earth, or a subway, or a tunnel. As I was writing, however, I realized that one of the most interesting aspects of the world that humans have constructed on the surface of the earth is the creation of mock or artificial underworlds in the sense of places that are meant to exclude organic life, where everything is meant to be a creation of human artifice rather than given from the larger universe. A shopping mall, for example, can serve as a model of a technological environment (a term Mumford didn’t use, but that I find useful) even if it isn’t literally underground.

But most of all I try to expand the concept of the underground from the earth to the sky. I end the book by comparing environmental consciousness with subterranean consciousness, pointing out that the real surface of the planet is the upper edge of the atmosphere. Our earthly home is everything below the frigid and uninhabitable realm of outer space, and so in a sense we have always lived below the surface of the planet, in a closed, finite environment.

more from Cabinet here.