1 The recent use of the term "pre-embryo" begs the question and was not used until it was found useful polemically in the ethical debates by those defending abortion or experimentation with embryos. We will ignore it in what follows and use only the older terms "zygote, embryo, and fetus." Note also the remark of Lee M. Silver: "I'll let you in on a secret. The term 'pre-embryo' has been embraced wholeheartedly by IVF practitioner, for reasons that are political, not scientific." Remaking Eden (New York: Avon Books, 1997), 39. [Back]
2 In current literature there is some ambiguity in the usage of the term "conception." Some follow the traditional meaning, as we do in this article, namely, as "fertilization: the onset of pregnancy" (Random House Dictionary of the English Language, The Unabridged Edition, 1983) while others mean by the term "the onset of pregnancy, marked by the implantation of the blastocyst" (see Dorland's Medical Dictionary, 26~ edition, 1 974). [Back]
3 On the history of this question, see John T. Noonan, Jr., "An Almost Absolute Value in History," in The Morality of Abortion: Legal and Historical Perspectives (Cambridge, Massachusetts: Harvard University Press, 1970), 1-59. [Back]
4 After the first commandment of love of God and neighbor the Didache in the "Two Ways of Life and Death" used to instruct persons for baptism says, "But the second commandment of the teaching is this "Thou shall do no murder; thou shalt not commit adultery ... thou shalt not procure abortion nor commit infanticide." Translation of Kirsopp Lake, The Apostolic Fathers, vol. ii, Loeb Classical Library (Cambridge, MA: Harvard University Press, 1985), 311 f. For the history of the Catholic Church on abortion, see John Connery, S. J., Abortion: The Development of the Roman Catholic Perspective (Chicago: University of Chicago Press, 1977). [Back]
5 Congregation for the Doctrine of the Faith, "Instruction on Respect for Human Life in its Origin and on the Dignity of Procreation: Replies to Certain Questions of the Day," 1987, I, (1). [Back]
6 See footnote 19, Declaration on Procured Abortion, Sacred Congregation for the Doctrine of the Faith (1974): "This declaration expressly leaves aside the question of the moment when the spiritual soul is infused. There is not unanimous tradition on this point and authors are as yet in disagreement. For some it dates from the first instant; for others it could not at least precede nidation. It is not within the competence of science to decide between these views, because the existence of an immortal soul is not a question in its field. It is a philosophical problem from which our moral affirmation remains independent for two reasons: 1) supposing a belated animation, there is still nothing less than a human life, preparing for and calling for a soul in which the nature received from the parents is completed; 2) on the other hand, it suffices that this presence of the soul be probable (and one can never prove the contrary) in order that the taking of life involve accepting the risk of killing a man, not only waiting for, but already in possession of a soul." [Back]
7 New York: Basic Books, 1988. [Back]
8 Notably Richard A. McCormick, "The Embryo Debate 3: The First 14 Days," The Tablet (10 March 1990), 301-304; "Who or What Is the Preembryo?" Kennedy Institute of Ethics Journal 1991, 1 (4): 1-15; "The Embryo As Potential: A Reply to John A. Robertson," ibid., 1991, 1 (4): 303-305. [Back]
9 New York: Oxford University Press, 1992. [Back]
19 Having a potentiality is something that is real but that is not here and now an actuality. A one-year-old human child has the potential of becoming an adult human -- unless impeded by disease or accident -- whereas a one-year-old chimp does not (even if raised by humans in a human environment), for it lacks this intrinsic potentiality. [Back]
21 "One cause [of spontaneous abortion of the conceptus] may be inadequate production of progesterone and estrogen by the corpus luteum." Keith L. Moore and T.V.N. Persaud, Before We Are Born: Essentials of Embryology and Birth Defects (Philadelphia, W.B. Saunders, 4th edition, 1993), 36. The authors place the rate of failure even higher, at forty-five percent. It is well to note that during the early years of this nation the death rate of infants under one year of age was about fifty percent. Does this minimize their intrinsic worth as human persons? [Back]
22 Morowitz and Trefil, 52-57. If the "strongest" scientific argument for a case can only be based on something not yet empirically demonstrated, the case is rather weak. [Back]
23 The most influential attempt by a Catholic author to revive this view was a philosopher, Joseph F. Donceel, S.J., "Immediate Animation and Delayed Hominization," Theological Studies 1970, 31(1): 71-105. [Back]
24 Norman Ford, When Did l Begin? Conception of the Human Individual in History, Philosophy and Science (Cambridge: University Press, 1991); Jason T. Eberl, Bioethics: Journal of the International Association of Bioethics, 14 (2) 2000: 134-157. [Back]
25 MZ [monozygotic or identical] twinning usually begins in the blastocyst stage around the end of the first week...and results from division of the inner cell mass or embryoblast into embryonic primordial," Moore and Persaud, Before We Are Born, 134. [Back]
26 Ford, When Did l Begin?, 84 f.; Eberl, "The Beginning of Personhood," 141. [Back]
27 Morowitz and Trefil, carefully define their terms (11-17), but for them "person" is a legal concept regarding human rights; "soul" is a religious concept and not a scientific one; and "humanness" has many meanings, so that the borderline between it and the pre-human is ill defined (19-20). We would define "person" as a being with the radical capacity for intellectual cognition and free choice. The term "soul" for Aquinas does not simply mean the human soul, but the form of any living thing, and the human soul one which enables a living thing to think and choose. Given these definitions, the question of the "humanness" of a living organism is whether it has a radical capacity to think and choose. This cannot, therefore, be a matter of degree, any more than whether an organism is alive or dead is a matter of degree. A living organism can have more or less vigorous life, and a human person more or less intelligence and freedom, but life and personhood are not arbitrarily distinguished from death and nonpersonhood. [Back]
28 For information on the medieval discussions of Aristotelian embryology see M. Anthony Hewson, Giles of Rome and the Medieval Theory of Conception: A Study of the "De formatione corporis human) in utero" (London: University of London Athlone Press, 1 975). [Back]
29 "The zygote is not the same ontological individual as either one of the eventual twins that result from its development, notwithstanding its genetic identity continuing throughout all its subsequent cleavages." When Did l Begin?, 119. Cloning, however, does not show that "ontological" individual A "ceases to exist" and that in its place two "ontological" individuals come into existence, but that A existed before B and continues to exist when B, derived from A, comes into existence. This holds also for the zygote as the A clone. The facts in no way show that it ceases to exist but simply that having lost a cell out of which B develops, it can by its regulative power supply this loss by again dividing. Of course, if twinning takes place at the two cell stage it may be arbitrary which of the two cells is called A as the immediate successor of the zygote and which B, since they come into existence simultaneously. If, however, further research demonstrates a polarity in the zygote, such as has been demonstrated in other mammalian species, as is probable, then that cell which contains the cytoplasm of the animal pole can properly be called A, that which contains the cytoplasm of the vegetal pole B, since the animal pole is more active (and thus anticipates the head or primary organ) than is the vegetal pole. [Back]
31 "In this context [of the discussion of how the egg or ovum is asymmetrical] 'animal' refers to typical animal organs such as eyes or the central nervous system, which often are formed in the vicinity of the egg's animal pole. The adjective 'vegetal' refers to the future 'vegetative organs' that derive from the primordial gut and serve 'lower' functions of life such as processing for food." Werner A. Müller, Developmental Biology (New York: Springer Verlag, 1997), 12. [Back]
32 "Mammalian and human embryos appear to leave the site where the inner cell mass will segregate to chance. The position of the inner cell mass defines the future dorsal side. How the head-tail polarity is specified is unknown." Müller, Developmental Biology, 169. [Back]
33 See Benedict M. Ashley, O.P. "A Critique of the Theory of Delayed Hominization," in D. G. McCarthy and A.S. Moraczewski, An Ethical Evaluation of Fetal Experimentation (St. Louis, MO: Pope John Center, 1976), Appendix I, 113-133; Benedict M.Ashley, O.P. and Albert S. Moraczewski, O.P., "Is the Biological Subject of Human Rights Present From Conception?" in Peter J. Cataldo and Albert S. Moraczewski, O.P., eds., The Fetal Tissue Issue: Medical and Ethical Aspects (Braintree, MA: Pope John Center, 1994). [Back]
34 Tristram Englehardt and others have actually argued in this vein, contending that personhood is a social construct. See his "Beginnings of Personhood: Philosophical Considerations," Perkins Journal of Theology 1973 (27): 20-27. [Back]
35 See Thomas Shannon and Alan Wolter, O.F.M., "Reflections on the Moral Status of the Pre-Embryo," Theological Studies 1990 (51): 603-626. [Back]