People and countries have done an enormous amount of damage in their attempts to bring about the best possible world. Communism is an obvious example. But so is British imperialism, which was not grubby self-interest all the way down, but at least in part a sincere attempt on the part of people who felt they were superior to other people to magnanimously improve the lot of their inferiors.

The idea that Bentham and Mill were maximizers is the greatest stretch of all. They were progressivists, committed to improving the societies in which they lived, not utopian maximizers.

Climate change involves behaviors that are individually negligible, whose impacts go far beyond the spatial and temporal constraints that define our sense of community.

The problem is that for almost any feature of humanity that you can name, whether it's the ability to suffer, whether it's the capacity to reason, whether it's having lives that can go better or worse, there are at least some other non-human animals that have all of these features as well. So to exclude non-human animals from the range of moral concern but to include all humans, just seems morally arbitrary.

One of the real dangers of our time is people's indifference to history.

It's possible that we'll screw up the climate so badly that most of us will die and a few breeding pairs will remain somewhere in the arctic. What's more likely is that we'll continue remaking the planet, driving many species to extinction, killing millions of people through the indirect effects of climate change, making life even harder for the poor and powerless than it is now, and making it a little more difficult for the global middle class to live the lives to which they have become accustomed - in other words, business as usual, only worse.

In trying to develop an impartial, expansive ethic we are trying to get ethical systems to do something which they did not evolve in order to do. This doesn't mean that it can't be done or that we shouldn't try to expand the reach of our ethical frameworks, only that there are reasons to be skeptical about its success.