Gregory Stock offers two sets of arguments against restricting future biotechnologies: first, that such rules are unnecessary as long as reproductive choices are being made by individual parents rather than states, and second, that they cannot be enforced and will be ineffective even if they were to be enacted. Let me respond to each in turn.

While genetic choices made by parents (either in the short run, via preimplantation genetic diagnosis, and in the more distant future, through germ-line engineering) are on the whole likely to be better than those made by coercive states, there are several grounds for not letting individuals have complete freedom of choice in this regard.

The first two are utilitarian. When we get into human germline engineering, safety problems will multiply exponentially over what we today experience with drug approval. Genetic causation is highly complex, with multiple genes interacting to create one outcome or behavior, and single genes having multiple effects. When a long-term genetic effect may not show up for decades after the procedure was administered, parents will risk a multitude of unintended and largely irreversible consequences for their children. This would seem to be, prima facie, a situation calling for strict regulation.

A second utilitarian concern has to do with possible negative externalities, which is the classic ground for state regulation, accepted by even the most orthodox free-market economists. An example is sex selection. Today in Asia, as a result of cheap sonograms and abortion, cohorts are being born with extremely lopsided sex ratios-117 boys for every 100 girls in China, and at one point 122 boys for every 100 girls in Korea. Sex selection is rational from the standpoint of individual parents, but imposes costs on society as a whole in terms of the social disruption that a large number of unattached and unmarriageable young males can produce. Similar negative externalities can arise from individual choices to, for example, prolong life at the cost of a lower level of cognitive and physical functioning.

A further set of concerns about the ability to "design" our children has to do with the ambiguity of what constitutes "improvement" of a human being, particularly when we get into attributes of personality and our emotional makeup. We are the product of a highly complex evolutionary adaptation to our physical and social environment, which has created an equally complex whole human being. Genetic interventions made out of faddishness, political correctness, or simple whim might upset that balance in ways that we scarcely understand-in the interests, for example, of making boys less violent and aggressive, girls more assertive, people more or less competitive, etc. Would an African-American's child be "improved" if we could genetically eliminate his or her skin pigmentation?

The final issue concerns human nature itself. Human rights are ultimately derived from human nature. That is, we assign political rights to ourselves based on our understanding of the ways members of our species are similar to one another, and different from other species. We are fortunate to be a relatively homogenous species: Earlier views that blacks were not intelligent enough to vote, or that women were too emotional to be granted equal political rights, proved to be empirically false. Greg Stock's final chapter opens up the prospect of a future world in which this human homogeneity splinters, under the impact of genetic engineering, into competing human biological kinds. What kind of politics do we imagine such a splintering will produce? The idea that our present-day tolerant, liberal, democratic order will survive these kinds of changes is far-fetched: Nietzsche, not John Stuart Mill or John Rawls, should be your guide to the politics of such a future.

Stock's second set of arguments concern his repeated assertions that no one can stop this technology. He is certainly right that if some future biotechnology proves safe, cheap, effective, and highly desirable, government would not be able to stop it and probably should not try. What I am calling for, however, is not a ban on wide swaths of future technology, but rather their strict regulation in light of the dangers outlined above.

We today regulate biomedical technology all the time. People can argue whether that technology is properly regulated and where exactly to draw various regulatory lines. But the argument that procedures that will be as potentially unsafe and ethically questionable as, say, germline engineering for enhancement purposes, cannot in principle be regulated, has no basis in past experience.

We slow the progress of science today for all sorts of ethical reasons. Biomedicine could advance much faster if we abolished our rules on human experimentation in clinical trials, as Nazi researchers did, and allowed doctors to deliberately inject infectious substances into their subjects. We today enforce rules permitting the therapeutic use of drugs like Ritalin, while prohibiting their use for enhancement (i.e., entertainment) purposes.

The argument that these technologies will simply move to more favorable jurisdictions if they are banned in any one country may or may not carry weight; it all depends on what they are and what the purpose of the regulation is. I regard a ban on reproductive cloning to be analogous to current legislation banning incest (indeed, many of the considerations are a virtually identical mix of safety and ethical reasons). The purpose of such a ban would not be undermined if a few rich people could get themselves cloned outside the country, and in any event, much of the world seems to be moving rather rapidly to a global reproductive cloning ban. The fact that the Chinese may not be on board shouldn't carry much weight; the Chinese involuntarily harvest organs from executed prisoners as well and are hardly an example we would want to emulate.

I don't think that a set of regulations designed to focus future biomedicine on therapeutic rather than enhancement purposes constitutes oppressive state intervention or goes so far beyond the realm of what is done today that we can declare its final failure in advance. Greg Stock is in effect saying that since rules against doping in athletic competitions don't work 100 percent of the time, we should throw them out all together and have our athletes compete in the future not on the basis of their natural abilities, but on the basis of who has the best pharmacologist. I'd rather watch and participate in competitions of the old-fashioned kind.