The usual way for new cells to come into being is by division of old cells. So the zygote, which is a—new—single cell formed from two, the sperm and ovum, is an exception. Textbooks of human genetics usually say that this new cell is beginning of a new human individual. What this indicates is that they suddenly forget about identical twins.

The usual way for new cells to come into being is by division of old cells. So the zygote, which is a—new—single cell formed from two, the sperm and ovum, is an exception. Textbooks of human genetics usually say that this new cell is beginning of a new human individual. What this indicates is that they suddenly forget about identical twins.

This paper analyzes the transformation from the human zygote to the implanted embryo under the prism of substantial change. After a brief introduction, it vindicates the Aristotelian ideas of substance and accident, and those of substantial and accidental change. It then claims that the transformation from the multicelled zygote to the implanted embryo amounts to a substantial change. Pushing further, it contends that this substantial change cannot be explained following patterns of genetic reductionism, emergence, and self-organization, and proposes Gustavo Bueno’s (...) idea of anamorphosis as a means to encapsulate criticism against such positions. (shrink)

Profoundly important ethical and political controversies turn on the question of whether biological life is an essential aspect of a human person, or only an extrinsic instrument. Lee and George argue that human beings are physical, animal organisms - albeit essentially rational and free - and examine the implications of this understanding of human beings for some of the most controversial issues in contemporary ethics and politics. The authors argue that human beings are animal organisms and that their personal identity (...) across time consists in the persistence of the animal organisms they are; they also argue that human beings are essentially rational and free and that there is a radical difference between human beings and other animals; criticize hedonism and hedonistic drug-taking; present detailed defenses of the prolife positions on abortion and euthanasia; and defend the traditional moral position on marriage and sexual acts. (shrink)

The topic of this book is material objects. Like most interesting concepts, the concept of a material object is one without precise boundaries.

When does a human being begin to exist? We argue that it is possible, through a combination of biological fact and philosophical analysis, to provide a definitive answer to this question. We lay down a set of conditions for being a human being, and we determine when, in the course of normal fetal development, these conditions are first satisfied. Issues dealt with along the way include: modes of substance-formation, twinning, the nature of the intra-uterine environment, and the nature of the (...) relation between fetus and mother (connection, parthood, dependence). (shrink)

This paper defends the permissibility of stem cell research against a theological objector who objects to it by appealing to "souls.".

What moral status should we attribute to stem cells? To answer this neglected question, we look in this essay at the properties of embryos and other entities that could develop into beings who have uncontested moral status, namely, adult humans. Our analysis indicates that those who grant moral status to embryos should also grant it to stem cells. This has implications that verge on absurdity, since even if we were to try to do what we can to protect these entities, (...) we would face the dilemma that the development of any embryo requires the destruction of other potential beings. We respond to objections, including the claim that the destruction of human embryos is wrong not because of the potential of human embryos but because human embryos are actual beings with a rational nature. We conclude that the more plausible position is to deny moral status to embryos, and thus to stem cells as well. (shrink)

Some philosophers argue that, because it is subject to twinning and fusion, the early human embryo cannot hold strong moral standing. Supposedly, the fact that an early human embryo can twin or fuse with another embryo entails that it is not a distinct individual, thus precluding it from holding any level of moral standing. I argue that appeals to twinning and fusion fail to show that the early human embryo is not a distinct individual and that these appeals do not (...) provide us with plausible reasons for denying the strong moral standing of the early human embryo. I recognize one possible exception to this general assessment, a particular version of the appeal to fusion. Embryo fusion that results in tetragametic chimerism provides some reason for doubting the early human embryo's moral standing. But twinning and fusion are otherwise irrelevant in this context. (shrink)

Assigning the appropriate moral status to different stages of human development is an urgent problem in bioethics. Many philosophers have attempted to assess developmental events using strict ontological principles to determine when a developing entity becomes essentially human. This approach is not consistent with recent findings in reproductive and stem cell biology, including the discovery of the plasticity of early embryonic development and the advent of induced pluripotent stem cells. Substance ontology should therefore not be used to determine the moral (...) status of the embryo. (shrink)

A comprehensive study of the ethics of killing in cases in which the metaphysical or moral status of the individual killed is uncertain or controversial. Among those beings whose status is questionable or marginal in this way are human embryos and fetuses, newborn infants, animals, anencephalic infants, human beings with severe congenital and cognitive impairments, and human beings who have become severely demented or irreversibly comatose. In an effort to understand the moral status of these beings, this book develops and (...) defends distinctive accounts of the nature of personal identity, the evaluation of death, and the wrongness of killing. The central metaphysical claim of the book is that we are neither nonmaterial souls nor human organisms but are instead embodied minds. In ethical theory, one of the central claims is that the morality of killing is not unitary; rather, the principles that determine the morality of killing in marginal cases are different from those that govern the killing of persons who are self‐conscious and rational. Another important theme is that killing in marginal cases should be evaluated in terms of the impact it would have on the victim at the time rather than on the value of the victim's life as a whole. What primarily matters is how killing would affect that which would be rational for the victim to care about at the time of death. By appealing to various foundational claims about identity, death, and the morality of killing, this book yields novel conclusions about such issues as abortion, prenatal injury, infanticide, the killing of animals, the significance of brain death, the termination of life support in cases of persistent vegetative state, the use of anencephalic infants as sources of organs for transplantation, euthanasia, assisted suicide, and advance directives in cases of dementia. In particular, the book defends the moral permissibility of abortion, infanticide, and euthanasia in certain cases and argues that brain death is not the appropriate criterion of death either for a person or a human organism. (shrink)

The main objection to human embryonic stem cell research is that it involves killing human embryos, which are essentially beings of the same sort that you and I are. This objection presupposes that we once existed as early embryos and that we had the same moral status then that we have now. This essay challenges both those presuppositions, but focuses primarily on the first. I argue first that these presuppositions are incompatible with widely accepted beliefs about both assisted conception and (...) monozygotic twinning. I then argue that we never existed as embryos. If this last claim is right, killing an embryo does not kill someone like you or me but merely prevents one of us from existing. (shrink)

One potentially valuable use of cloning is to provide a source of tissues or organs for transplantation. The most important objection to this use of cloning is that a human clone would be the sort of entity that it would be seriously wrong to kill. I argue that entities of the sort that you and I essentially are do not begin to exist until around the seventh month of fetal gestation. Therefore to kill a clone prior to that would not (...) be to kill someone like you or me but would be only to prevent one of us from existing. And even after one of us begins to exist, the objections to killing it remain comparatively weak until its psychological capacities reach a certain level of maturation. These claims support the permissibility of killing a clone during the early stages of its development in order to use its organs for transplantation. (shrink)

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. (shrink)

From fertilization to approximately the sixteenth day of development, human embryonic cells are said to have the capacities of totipotency and monozygotic twinning, both of which are problematic to a theory of ensoulment at fertilization. In this article I will address the problems which these capacities pose to such a theory and present an interpretation of the biological data which renders ensoulment at fertilization more plausible. I will then argue that not only is an ensoulment theory consistent with current biological (...) data on the human embryo, but it may offer an explanation for the phenomencon of monozygotic twinning. (shrink)

When Did I Begin? investigates the theoretical, moral, and biological issues surrounding the debate over the beginning of human life. With the continuing controversy over the use of in vitro fertilization techniques and experimentation with human embryos, these issues have been forced into the arena of public debate. Following a detailed analysis of the history of the question, Reverend Ford argues that a human individual could not begin before definitive individuation occurs with the appearance of the primitive streak about two (...) weeks after fertilization. This, he argues, is when it becomes finally known whether one or more human individuals are to form from a single egg. Thus, he questions the idea that the fertilized egg itself could be regarded as the beginning of the development of the human individual. The author also differs sharply, however, from those who would delay the beginning of the human person until the brain is formed, or until birth or the onset of conscious states. (shrink)