First, a personal confession: A few years back, the business of being a good environmentalist seemed, to me, a straightforward affair. As I weighed one issue after another, the world could be seen in just two colors””green and ungreen””which corresponded to two moral states: good and ungood. It was easy to distinguish one from the other. My thinking would run along lines like this: Trees are good, so the companies that chop them down are not. Or like this: Rivers are polluted, so the fault must lie with the most obvious, nefarious-looking suspect””discharge pipes at waterside factories.