Today if you look at most economic textbooks, economics is not defined by subject matter. It's presented as a science of social choice that applies not only to material goods - not only to flat-screen televisions - but to every decision we make, whether it's to get married, or to stay married, whether to have children and how to educate those children, or how to look after our health.

My argument is not that we must never intervene in nature. My argument is that there is a moral difference between intervention for the sake of health, to cure or prevent disease, and intervention for the sake of achieving a competitive edge for our kids in a consumer society.

There is a tendency to think that if we engage too directly with moral questions in politics, that's a recipe for disagreement, and for that matter, a recipe for intolerance and coercion.

Whether you're a libertarian liberal or a more egalitarian liberal, the idea is that justice means being non-judgmental with respect to the preferences people bring to public life.

It's possible to make sense of what's morally at stake in an appreciation of the gift of life, or the gift of a child, without necessarily presupposing that there is a giver. What matters is that the gift - in this case, the child - not be wholly our own doing, our own product.

Most economics that is taught in college and universities today projects itself as a value-neutral science. This claim has always been open to question, but I think it's especially in doubt today.

I'm a supporter of embryonic stem cell research. I do think there are very important moral and also religious questions at stake in the debate over embryonic stem cell research.