The ontological status of embryos: a reply to Jason Morris.

In various places we have defended the position that a new human organism, that is, an individual member of the human species, comes to be at fertilization, the union of the spermatozoon and the oocyte. This individual organism, during the ordinary course of embryological development, remains the same individual and does not undergo any further substantial change, unless monozygotic twinning, or some form of chimerism occurs. Recently, in this Journal Jason Morris has challenged our position, claiming that recent findings in reproductive and stem cell biology have falsified our view. He objects to our claim that a discernible substantial change occurs at conception, giving rise to the existence of a new individual of the human species. In addition, he objects to our claim that the embryo is an individual, a unified whole that persists through various changes, and thus something other than a mere aggregate of cells. Morris raises a number of objections to these claims. However, we will show that his arguments overlook key data and confuse biological, metaphysical, and ethical questions. As a result, his attempts to rebut our arguments fail.

Human cloning and embryo research: the 2003 John J. Conley Lecture on medical ethics.

The author, a member of the U.S. President's Council on Bioethics, discusses ethical issues raised by human cloning, whether for purposes of bringing babies to birth or for research purposes. He first argues that every cloned human embryo is a new, distinct, and enduring organism, belonging to the species Homo sapiens, and directing its own development toward maturity. He then distinguishes between two types of capacities belonging to individual organisms belonging to this species, an immediately exerciseable capacity and a basic natural capacity that develops over time. He argues that it is the second type of capacity that is the ground for full moral respect, and that this capacity (and its concomitant degree of respect) belongs to cloned human embryos no less than to adult human beings. He then considers and rejects counter-arguments to his position, including the suggestion that the capacity of embryos is equivalent to the capacity of somatic cells, that full human rights are afforded only to human organisms with functioning brains, that the possibility of twinning diminishes the moral status of embryos, that the fact that people do not typically mourn the loss of early embryos implies that they have a diminished moral status, that the fact that early spontaneous abortions occur frequently diminishes the moral status of embryos, and that his arguments depend upon a concept of ensoulment. He concludes that if the moral status of cloned human embryos is equivalent to that of adults, then public policy should be based upon this assumption.