But our desires for a better life do not end with health, and the possibilities of biotechnology are not limited to therapy. Although most biomedical technologies are developed for therapeutic purposes, once here they are quickly available to serve many other ends, good ones and bad. And the powers they provide to alter the workings of body and mind -- the very essence of biomedical technology -- are attractive not only to the sick and suffering but to everyone who desires to look younger, perform better, feel happier or become more "perfect."

Some of our most popular dreams and nightmares -- such as a world of genetically engineered "designer babies," with parents ordering up their children's characteristics -- are scientifically unlikely. But other scenarios are more than plausible, and many desire-satisfying uses of biotechnology are already here: embryo screening or sperm-sorting to choose the sex of offspring; growth hormone to make children taller; Ritalin and similar drugs to control behavior or boost performance in the young, and Prozac and similar drugs to brighten moods or alter temperaments -- not to mention Botox, Viagra or anabolic steroids. Many of these technologies are used mostly for good medical reasons. But not simply and not always.

Looking ahead, other biotechnical powers are already visible on the horizon: Drugs to flatten the emotional tone of painful or shameful memories. Genes to increase the size and strength of muscles. Nano-mechanical implants to enhance sensation or motor skills. And perhaps techniques to slow biological aging and increase the maximum human life span.

All this leaves us wondering: What's the problem? What could be wrong with seeking better children, superior performance, ageless bodies and happy souls? These are, after all, old and often worthy human desires, which biotechnology promises to help us satisfy more easily. Moreover, in free societies such as ours, choices about using technical enhancers of this kind are not made by central planners pursuing some vision of a perfect future society. They are made largely by private individuals pursuing their personal dream of happiness, for themselves and for their children. Why worry, then, about letting people decide for themselves which uses of drugs or devices, serving which goals, are right for them?

To be sure, there are questions about the safety of new biotechnologies and about equality of access to their use. But these familiar concerns do not reach either the true promise or deeper perils of the biotechnology revolution. Our hopes for self-improvement and our disquiet about a "post-human" future are much more profound. At stake are the kind of human being and the sort of society we will be creating in the coming age of biotechnology.

On the optimistic view, the emerging picture is one of unmitigated progress and improvement. It envisions a society in which more and more people are able to realize the American dream of liberty, prosperity and justice for all. It is a nation whose citizens are longer-lived, more competent, better accomplished, more productive and happier than human beings have ever been. It is a world in which many more human beings -- biologically better-equipped, aided by performance-enhancers, liberated from the constraints of nature and fortune -- can live lives of achievement, contentment and high self-esteem, come what may.

But there are reasons to wonder whether life will really be better if we turn to biotechnology to fulfill our deepest human desires. There is an old expression: To a man armed with a hammer, everything looks like a nail. To a society armed with biotechnology, the activities of human life may seem more amenable to improvement than they really are. Or we may imagine ourselves wiser than we really are. Or we may get more easily what we asked for only to realize it is much less than what we really wanted.

We want better children -- but not by turning procreation into manufacture or by altering their brains to give them an edge over their peers. We want to perform better in the activities of life -- but not by becoming mere creatures of our chemists or by turning ourselves into tools designed to win and achieve in inhuman ways. We want longer lives -- but not at the cost of living carelessly or shallowly with diminished aspiration for living well, and not by becoming people so obsessed with our own longevity that we care little about the next generations. We want to be happy -- but not because of a drug that gives us happy feelings without the real loves, attachments and achievements that are essential for true human flourishing.

For the past 16 months, the President's Council on Bioethics has explored the ethical and social meanings of using biotechnologies for purposes "beyond therapy." Our report, released today, tries to show what is increasingly at stake when biotechnology meets the pursuit of happiness. Lacking prophetic powers, no one can say for certain what life in the age of biotechnology holds in store. Most likely it will be the usual mix of unforeseen burdens and unexpected blessings. But we must begin thinking about these issues now, lest we build a future for ourselves that cheapens, rather than enriches, America's most cherished ideals.

The writer is chairman of the President's Council on Bioethics and the Hertog Fellow at the American Enterprise Institute.