Lewis' early academic focus was on the interplay between economic development,
environmental degradation, and cultural change in the highlands of northern Luzon in the Philippines, explored in his dissertation and first book. He also wrote on environmental philosophy. His 1992 book
Green Delusions: An Environmentalist Critique of Radical Environmentalism is often seen as a forerunner of
the ecomodernist movement. As of 2024, Lewis is a senior scholar at the Breakthrough Institute. and served as the former associate editor of The Geographical Review. After teaching at
George Washington University and
Duke University, Lewis joined Stanford in 2002, studying and writing mostly about global geography. His interest in historical geography led to work on historical linguistics, culminating in the publication of
The Indo-European Controversy (with linguist
Asya Pereltsvaig) in 2015. Lewis publishes a blog called GeoCurrents that examines a wide variety of geographical and historical topics and includes many original maps. ==Views on metageography and postmodernism==