Prospects for "genetic therapy" -- can a person benefit from being altered?

Mapping the human genome is an immense project with numerous objectives. Indeed, it is likely that some of its most important ramifications and applications remain as yet unglimpsed. All we can presently attempt is to focus on some of the more obvious possibilities and prepare for the problems already looming on our horizon. One such possibility is that of Prenatal Genetic Intervention (PGI), which might be said to be a therapeutic intervention on behalf of the embryonic child. In this paper, I argue that "genetic therapy" is likely to be a misnomer, and that if PGI becomes possible, we should generally resist its inclusion under the special moral duty of providing health care. "Therapy" necessarily means helping a person, while PGI -- though effecting improvements from an impersonal perspective -- will frequently not consist in directly helping any person. This is due not to the embryo not being a person, but rather to the basic philosophical problem of personal identity persisting through significant alterations -- especially the alteration of genotype. The decisive moral question then hinges on the definition of "significant" alteration. I shall examine the feasibility of drawing analogies from criteria for personal identity proposed in discussions of how persons maintain their identity across time and through physical and psychological change. Certain metaphysical aspects of human identity and individuality will be also touched upon, partly in terms derived from classical Judaism. In conclusion I argue that, regarding embryos in particular, persistence of genotype must generally be deemed a necessary condition for maintaining personal identity. Therefore, many proposals for PGI should be excluded from the notion of therapeutic intervention and thus denied the special moral status of requests for therapy.