The mere mention of genetic enhancement makes many people cringe and brings to mind the Nazi eugenics programs, Aldous Huxley’s Brave New World, “The X‐Files,” or the recent movie “Gattaca.” Although many people believe that gene therapy has morally legitimate medical uses,17,18 others regard genetic enhancement as morally problematic or decidedly evil.19–21
The purpose of this essay is to examine the moral significance of the therapy–enhancement distinction in human genetics. Is genetic enhancement inherently unethical? Is genetic therapy inherently ethical? I will argue that the distinction does not mark a firm boundary between moral and immoral genetic interventions, and that genetic enhancement is not inherently immoral. To evaluate the acceptability of any particular genetic intervention, one needs to examine the relevant facts in light of moral principles. Some types of genetic therapy are morally acceptable while some types of genetic enhancement are unacceptable. In defending this view, I will discuss and evaluate several different ways of attempting to draw a solid moral line between therapy and enhancement.22
Somatic versus Germline Interventions
Before discussing the therapy–enhancement distinction, it is important that we understand another distinction that should inform our discussion, viz. the distinction between somatic and germline interventions.23,24 Somatic interventions attempt to modify somatic cells, while germline interventions attempt to modify germ cells. The gene therapy clinical trials that have been performed thus far have been on somatic cells. If we combine these two distinctions, we obtain four types of genetic interventions:
1 Somatic genetic therapy (SGT)
2 Germline genetic therapy (GLGT)
3 Somatic genetic enhancement (SGE)
4 Germline genetic enhancement (GLGE)
While I accept the distinction between somatic and germline interventions, it is important to note that even interventions designed to affect somatic cells can also affect germ cells: current SGT trials carry a slight risk of altering germ cells.25 Even so, one might argue that this is a morally significant distinction because somatic interventions usually affect only the patient, while germline interventions are likely to affect future generations.26 In any case, the therapy–enhancement distinction encompasses somatic as well as germline interventions, and my discussion of this distinction will include both somatic as well as germline interventions.
The Concepts of Health and Disease
Perhaps the most popular way of thinking about the moral significance of the therapy–enhancement distinction is to argue that the aim of genetic therapy is to treat human diseases while the aim of genetic enhancement is to perform other kinds of interventions, such as altering or “improving” the human body.27–29 Since genetic therapy serves morally legitimate goals, genetic therapy is morally acceptable; but since genetic enhancement serves morally questionable or illicit goals, genetic enhancement is not morally acceptable.30–33 I suspect that many people view the distinction and its moral significance in precisely these terms. W. French Anderson states a clear case for the moral significance of genetic enhancement:
On medical and ethical grounds we should draw a line excluding any form of genetic engineering. We should not step over the line that delineates treatment from enhancement.34
However, this way of thinking of medical genetics makes at least two questionable assumptions: (1) that we have a clear and uncontroversial account of health and disease, and (2) that the goal of treating diseases is morally legitimate, while other goals are not. To examine these assumptions, we need to take a quick look at discussions about the concepts of health and disease.
The bioethics literature contains a thoughtful debate about the definitions of health and disease and it is not my aim to survey that terrain here.35,36 However, I will distinguish between two basic approaches to the definition of health, a value‐neutral (or descriptive) approach and a value‐laden (or normative) one.37 According to the value‐neutral approach, health and disease are descriptive concepts that have an empirical, factual basis in human biology. Boorse defended one of the most influential descriptive approaches to health and disease: a diseased organism lacks the functional abilities of a normal member of its species.38 To keep his approach value‐neutral, Boorse interprets “normal” in statistical terms, i.e., “normal” = “typical.” Daniels expands on Boorse’s account of disease by suggesting that natural selection can provide an account of species‐typical functions: functional abilities are traits that exist in populations because they have contributed to the reproduction and survival of organisms that possessed them.39 Thus a human with healthy lungs has specific respiratory capacities that are normal in our species, and these capacities have been “designed” by natural selection. A human who lacks these capacities, such as someone with cystic fibrosis or emphysema, has a disease.
According to the value‐laden approach, our concepts of health and disease are based on social, moral, and cultural norms. A healthy person is someone who falls within these norms; a diseased person deviates from them. Someone who deviates from species‐typical functions could be considered healthy in a society that views that deviation as healthy: although schizophrenia has a biological basis, in some cultures schizophrenics are viewed as “gifted” or “sacred,” while in other cultures they are viewed as “mentally ill.” Likewise, some cultures view homosexuality as a disease, while others do not.40–42
Many different writers have tried to work out variants on these two basic approaches to health and disease, and some have tried to develop compromise views,43,44 but suffice it to say that the first assumption mentioned above – i.e., that we have a clear and uncontroversial account of health and disease – is questionable.
Even if we lack an uncontroversial account of disease, we could still ask whether either of the two basic approaches would condemn genetic enhancement unconditionally. Consider the descriptive approach first. If statements
