Some or one gene is identified as the cause of such disease and doctors will try to replace it with a normal gene, or, if our techniques improved far enough, to restore it so that our body functions normally again. If this is done upon a patient who suffers the disease, which is incurable, by other means, it seems obvious that it should be done. As long as this is done in similar fashion like what we have been doing in the usual type of therapy, it is not only objectionable, but should be morally approved. For Confucians, gene therapy as a way of making up for the defects of Nature, it is by all means a moral one. Even for cases of genetic manipulations or changes, Confucians will not think that it is anything bad just because it looks like playing God.
Gene therapy brings along with it another closely related practice, that is, negative eugenic.
By gene therapy, we are getting rid of some of our bad genes through our treatment and thus eliminate them from our body once for all. It comes very close to negative eugenic in that the latter is in a sense the eradicating of people with bad genes. Formerly, we do not have the technology for replacing the genes, so we replaced the people, that means sending the patients to gas chamber. Now we have the treatment that could get rid of the bad genes, we change the genetic constitution of the patient. However, there are always genetic diseases that could not be replaced, or replaced with high cost.