In its most basic form, the central argument supporting the claim that it is unethical to destroy human embryos goes as follows: It is morally impermissible to intentionally kill innocent human beings; the human embryo is an innocent human being; therefore it is morally impermissible to intentionally kill the human embryo.
It is worth noting that this argument, if sound, would not suffice to show that all or even most HESC research is impermissible, since most investigators engaged in HESC research do not participate in the derivation of HESCs but instead use cell lines that researchers who performed the derivation have made available.
While each of the cells is alive, they only become parts of a human organism when there is substantial cell differentiation and coordination, which occurs around day-16 after fertilization.
Thus, on this account, disaggregating the cells of the 5-day embryo to derive HESCs does not entail the destruction of a human being.
At this stage, human embryos are said to be “whole living member[s] of the species homo sapiens …
[which] possess the epigenetic primordia for self-directed growth into adulthood, with their determinateness and identity fully intact” (George & Gomez-Lobo 2002, 258).However, most of those who oppose the research argue that the constraints against killing innocent persons to promote social utility apply to human embryos.Thus, as long as we accept non-consequentialist constraints on killing persons, those supporting HESC research must respond to the claim that those constraints apply to human embryos.However, it does not follow that the zygote is not a human being, or that it has not individuated.This would follow only if one held that a condition of an entity’s status as an individual human being is that it be impossible for it to cease to exist by dividing into two or more entities. Consider cases in which we imagine adult humans undergoing fission (for example, along the lines of Parfit’s thought experiments, where each half of the brain is implanted into a different body) (Parfit 1984).The potential therapeutic benefits of HESC research provide strong grounds in favor of the research.If looked at from a strictly consequentialist perspective, it’s almost certainly the case that the potential health benefits from the research outweigh the loss of embryos involved and whatever suffering results from that loss for persons who want to protect embryos.This process of disaggregating the blastocyst’s cells eliminates its potential for further development.Opponents of HESC research argue that the research is morally impermissible because it involves the unjust killing of innocent human beings.The prospect of our going out of existence through fission does not pose a threat to our current status as distinct human persons.Likewise, one might argue, the fact that a zygote may divide does not create problems for the view that the zygote is a distinct human being.