I do not argue that nature is sacrosanct in the sense that we must never tamper with nature. That would disempower, really, all of medicine. That would mean that we can't combat dread diseases - malaria, polio, all of which are given by nature, if one thinks about it.

A better way to mutual respect is to engage directly with the moral convictions citizens bring to public life, rather than to require that people leave their deepest moral convictions outside politics before they enter.

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.

I think the reason we might hesitate to pay cash to students for doing well on tests or getting good grades or reading books is that we sense that the monetary payment is an extrinsic reward.

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.

One can imagine a kind of hormonal arms race or genetic arms race, whether it's to do with height or IQ, conceivably, in the future. So it's limitless, and that's another of the features that sets it apart from medical intervention.

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.