Environmentalists like to advocate what they call “green living”, which doesn’t mean dressing up like a leprechaun or Kermit the Frog. But how nice is “nature” anyway? The philosopher David Hume said that, of all words, “there is none more ambiguous and equivocal” than “nature”. Some people speak of “nature” as a benign friend to the “economy”, a source of “natural capital” and “natural wealth”. But nature also seems to be an inscrutable source of “natural disasters” — even if some “natural disasters”, like Hurricane Katrina, are made much worse because they are also human disasters caused by bad planning and response, and subsequently blamed on a “nature” who can’t talk back.