Markets are useful instruments for organizing productive activity. But unless we want to let the market rewrite the norms that govern social institutions, we need a public debate about the moral limits of markets.

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.

I am trying to get at the moral arguments and the ethical status of various attempts at enhancement, or genetic engineering, or the bid for designer children. But there are implications for society at large.

If you go back to Adam Smith, you find the idea that markets and market forces operate as an invisible hand. This is the traditional laissez-faire market idea. But today, when economics is increasingly defined as the science of incentive, it becomes clear that the use of incentives involves quite active intervention, either by an economist or a policy maker, in using financial inducements to motivate behavior. In fact, so much though that we now almost take for granted that incentives are central to the subject of economics.

The relief of suffering is a great good. The curing of illness and disease - these are great human goods. This is the mission of medicine.

In most of our lives, we are accustomed to aiming at mastery and control and dominion- - over nature, over our lives, over our jobs, over our careers, over the goods that we buy.

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.