The idea that we would raise billions of sentient animals, treat them horribly, pollute our waterways with their waste, compromise the effectiveness of our antibiotics so that they grow faster, and then slaughter them with little regard to their suffering so that we can feed off their corpses, will seem to most people unthinkably cruel and barbarous - sort of in the way that we think of medieval punishments, or Europeans today think of the death penalty.

I begin with human psychology and then see what we can say about ethics.

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."

We're highly adaptable and have developed some powerful systems of representation.

Citizens often think of a state's interests in terms of the promotion of ideals such as democracy, a particular way of life, or other values which they endorse or see as part of their historical continuity and identity. In this domain as in others values are not fixed, and so a state's interests are dynamic and in a constant state of negotiation and construction.

I think the mother of all arguments against eating meat now is the climate change argument. Methane is a much more powerful greenhouse gas than carbon dioxide and when we eat meat we wipe away many of the good things that we do when we try to create greener and more sustainable practices in the rest of our lives. So if you add the concern for climate change with other concerns that were there. I think the case for vegetarianism is pretty overwhelming.

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.