Sean Carroll in Preposterous Universe:
We all know you can’t derive “ought” from “is.” But it’s equally clear that “is” — how the world actual works — is going to matter for “ought” — our moral choices in the world. And an important part of “is” is who we are as human beings. As products of a messy evolutionary history, we all have moral intuitions. What parts of the brain light up when we’re being consequentialist, or when we’re following rules? What is the relationship, if any, between those intuitions and a good moral philosophy? Joshua Greene is both a philosopher and a psychologist who studies what our intuitions are, and uses that to help illuminate what morality should be. He gives one of the best defenses of utilitarianism I’ve heard.