Once again, we are saddled with a Stone Age moral psychology that is appropriate to life in small, homogeneous communities in which all members share roughly the same moral outlook. Our minds trick us into thinking that we are absolutely right and that they are absolutely wrong because, once upon a time, this was a useful way to think. It is no more, though it remains natural as ever. We love our respective moral senses. They are as much a part of us as anything. But if we are to live together in the world we have created for ourselves, so unlike the one in which our ancestors evolved, we must know when to trust our moral senses and when to ignore them.

--Joshua Greene