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.

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.

A market economy is a tool - a valuable and effective tool - for organizing productive activity. A market society is a way of life in which market values seep into every aspect of human endeavour. It's a place where social relations are made over in the image of the market.

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.

It's true that to speak of an ethic of giftedness, which is very much the ethic that I deploy in raising questions about designer children and genetic engineering - an appreciation of the giftedness of the child or the giftedness of life does have religious resonance, because a great many religious traditions emphasize the sense in which the good things in life are not all our own doing; they are gifts from God.

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.

First, individual rights cannot be sacrificed for the sake of the general good, and second, the principles of justice that specify these rights cannot be premised on any particular vision of the good life. What justifies the rights is not that they maximize the general welfare or otherwise promote the good, but rather that they comprise a fair framework within which individuals and groups can choose their own values and ends, consistent with a similar liberty for others.