Environmental problems provoke challenges about what kind of world we want, how important we think it is if something is brought about by human action or by brute nature, what we think of the value of human life compared to that of other living things.

Ethical systems are fundamentally conservative and primarily directed towards regulating interactions within communities.

I think when it comes to climate change, the single most important thing in the world is for the United States' Congress to pass an effective bill that will put a price in carbon because if it starts costing something to emit carbon, this will provide an incentive, people do act on the basis to some extent of economic incentives to emit fewer greenhouse gases.

Since for me moral demands necessarily flow from human psychology, I don't think we can be obliged to do something that we are not motivated in any way to do. In other words, I'm an "internalist" about morality.

We need to use economic instruments such as carbon taxes, cap and trade, tax and dividend and whatever else to help incentivize behavior that will move us to a post-carbon, post-animal agriculture world, and make our societies more resilient to the shocks that are already baked into the system. But that doesn't make climate change an "economic issue."

Acts are right in virtue of the goodness of their consequences.

Well, one measure of a good life, I think, is to be engaged in projects that one thinks are meaningful and worthwhile. So I would put the emphasis of a good life on activity, on the walk rather than the destination, and I think that most of the things that any of us do that are really valuable and really important are projects that we really shouldn't expect to be completed in our lifetime because if they could completed in our lifetime, they probably wouldn't be so important that we should devote our lives to them.