December 4, 2001 -- In the coming months, ethicists will be variously defending or condemning human cloning and embryonic stem cell research. They will debate the potential benefits of the technology and discuss the social consequences of the advancing science. But in the end, the ethical question will turn on the issue of when a human life begins—i.e., the life of a distinct, individual human being, a person.
There is no simple answer, because the different dimensions of a person's identity emerge at different points in a continuous and complex process of development. Genetic identity is present in the fertilized egg. Cognitive identity emerges later when the fetus acquires the neural basis for conceptual thought. Biological identity as a distinct organism begins to emerge at the point of viability, and is fully present at birth. The person's moral identity as a being capable of voluntary choice on the basis of knowing right from wrong, and his spiritual identity as a self-consciously differentiated personality, are both later developments of childhood and adolescence.
While there can be honest philosophical disagreement about the moment at which personhood begins, there is no rational basis for pushing that point all the way back to conception. It is true that the zygote is the first stage at which the genetic identity of the person-to-be is fully determined, and that fertilization initiates the processes of cell division that will ultimately produce a new human being. But it is also true that a single zygote can divide to produce twins, and also that it may naturally fail to develop at all. And even if it does, there are many other factors during pregnancy that affect the biological nature and viability of the fetus. Fertilization is but one of many, many necessary steps on the way to personhood.
The most important consideration, however, is humanity’s essential nature as a rational animal. In regard to our animal nature, the key development is the ability to initiate action in support of our lives; in regard to reason, it is the development of the cortical areas in the brain. It is only when those areas are fully developed—sometime during the later stages of pregnancy—that the fetus becomes a person. Stem cell research, and cloning of embryos for that research, uses blastocysts of only about 100 cells. This stage occurs within a few days after fertilization, long before anyone could rationally attribute a distinct individual identity in any but the barest genetic sense.
On the other hand, the prospect of creating embryos deliberately for the purpose of research—for the purpose of manipulating them, extracting value, and then discarding what's left—troubles many people. Scientists would be creating something that might develop into a person in order to use it as a means of helping other people. Those who are troubled by this feature of the research may be reacting on the basis of the rational principle that individuals are ends in themselves, not means to be sacrificed for the ends of others. But the individualist principle applies to people, not blastocysts.
As for the spiritual side of the issue, cloning and stem cell research, like all technology, extend humanity’s choices. And it is the extension of choice and the pursuit of knowledge that offer us the opportunity to expand the boundaries of our existence. Our human spirit, that within us that searches for truth and asks questions about morality, that part of our mind that aspires and dreams—our soul—is ultimately the product of our own design. A human spirit is not a gift or an accident, but the product of a lifetime's work. A soul is the willful product of rationality, the manifestation of the conceptual mind. That soul is present neither in the blastocyst, the zygote, or the embryo—it is manifest only in a person.
An embryo is not a person, not by a long shot.