In this letter published in The New Yorker, Amory Lovins responds to David Owen’s article about energy efficiency and Jevons Paradox. This letter was published in the January 17, 2010 issue of The New Yorker and is reprinted with kind permission of the magazine. The original article, “The Efficiency Dilemma,” by David Owen, can be found at The New Yorker (subscription required). Copyright © 2011. Courtesy of The New Yorker.