Remaking ourselves? The ethics of stem-cell research

Commonweal, Dec 4, 1998 by Thomas A. Shannon

In the first week of November, articles in both Science and the Proceedings of the National Academy of Science reported the stunning news that human stem cells have been isolated and cultivated. These cells are the precursors of the entire human body. The capacity to isolate and cultivate them means that we have the potential ability to produce tissue in the laboratory for use in generating new tissue, in developing new organs for transplantations, as well as cells for use in gene therapy.

In one line of research, the cells were taken from the inner cell mass of the blastocyst stage - one of the earliest stages in the development of the human preimplantation embryo. It is from these undifferentiated cells that the entire embryo and fetus will develop. These particular blastocyst cells were taken from preimplantation embryos left over from fertility treatments that were not going to be used in further in vitro fertilization attempts. In the second line of research, using aborted fetuses, the cells were taken from their embryonic germ cells that would not develop into specific body parts but into new eggs or sperm.

Herein lies the nub of the ethical issue: What is the moral status of the very early human embryo and of the tissue of an aborted fetus? In both lines of research, the teams of scientists recognize that the cells do have moral status since they come from human embryonic material. While I agree totally, 1 see a distinction between those cells drawn from the human preimplantation embryo and those obtained from aborted fetuses. While I do not agree with them, the group working on embryonic germ cells (the ones from aborted fetuses) claims that the use of these cells presents no particular problem because such cells could not be the precursor of a fetus; even so, they too recognize the special status of the human tissue.

I would argue that because the process of what biologists call differentiation has not yet occurred in the preimplantation embryo, such an entity is not individualized; it therefore lacks a core feature of personhood. This is so for two reasons: First, the cells in this entity have the capacity to become some (pluripotent) or any (totipotent) part of the body - and therefore the preimplantation embryo cannot be understood to be a single individual. For by definition, an individual is an entity that cannot be divided or, if it is, it becomes two halves neither of which can survive on its own. Second, the cells of the preimplantation embryo can be separated without harm to the organism (for example, in preimplantation diagnosis, one or two cells can be removed and examined for genetic disease). Further, the cells can be divided artificially to form twins. Finally, each of the cells has the potential to be another whole individual. My argument is that since the entity at this stage is not yet individualized, it lacks a critical, though not the only, criterion for personhood.

So how might we think of such an entity? Let me suggest an idea developed by the medieval philosopher Duns Scotus, though, of course, he had no clue about stem cells. His concept may help us get a handle on how to think about this entity in order to come to some ethical resolution about the development and use of embryonic stem cells. This argument does not apply to the use of embryonic germ cells, that is, to cells obtained from aborted fetuses, because individuation has already happened.

Scotus uses the term "common nature" to describe what is common to both the group and the individual. The term is part of his larger theory of knowledge and individualization. "Common nature" is essentially the basis for the definition of any entity, what all horses share in common, for example. But what horses share in common is indifferent to whether we are referring to a singular horse or to all horses. For Scotus, then, the common nature needs something else - an individualizing principle - to constitute a particular horse. Scotus's principle of individuation constricts, as he says, the form of this common nature into an individual, rendering this being unique, distinct from all others of the same species, and indivisible. In short, it has a singular unity; it is incapable of being divided into two wholes.

We can think of the preimplantation embryo as our common human nature for two reasons. First, even though this entity, is genetically distinct from its parents and even genetically unique, it is not yet individualized. Individualization does not occur until after the process of restriction is completed, some two weeks after the process of fertilization. To my mind, this process is a biological analogy to Scotus's concept of the principle of individuation, the constricting of the common nature into an individual. After the process is completed (normally after two weeks), the cells are committed to being specific cells in specific body parts. This is the biological beginning of true (though not full) individuality and, I would argue, marks a critical ethical line.