Ecology is the logic of living creatures in their homes. Ecology mixes with ethics, an ecological (or environmental) ethics urging that humans ought to find a lifestyle more harmonious with nature. Humans have always had to rest their cultures on a natural life support system. Environmental engineers may now claim that the principal novelty of the new millennium is that Earth will be a managed planet. Such claims bring increasing concern how far nature can and ought be transformed into humanized nature. Thinking of humans as fitting themselves into a sustainable biosphere is a better logic of being at home on Earth.