1 A note on terminology: By ‘human being’ I mean any animal which is a member of the species homo sapiens. A human baby is an animal which is a member of homo sapiens, when it is young, and a human fetus is an animal which is a member of homo sapiens, when it is still younger. The fetus is simply a very young human being: this much follows from modem biology and embryology. But it cuts no moral ice. The mere fact that a creature is a member of a particular species does not entail that it has (or lacks) a right to life. The question is: When and in virtue of what do members of the species homo sapiens (human beings) acquire a right to life? This doesn't answer itself.

2 Sumner, L.W. Abortion and Moral Theory (Princeton, NJ: Princeton University Press 1981) 104CrossRefGoogle Scholar

3 The embryo can produce different animals too: if the blastula divides it will produce two animals, neither of which is identical to the animal it actually produces. But then doesn't the last argument show that the embryo isn't identical to the animal it actually produces? That argument depends upon the premiss ‘If the sperm is identical to the zygote it in fact produces, then (by parity of reasoning) it would be identical to the zygote it would produce if it combined with a different egg’; plainly this premiss is true. But it is false that if the embryo is identical to the animal it actually produces, then (by parity of reasoning) it would be identical to the animals if would produce if it divided; one cannot be two. So the argument fails for the embryo.

4 We might try to blunt this point by denying that the human animal is an animal at its earliest stage: these four entities aren't animals though two will become animals if they survive. But this is entirely ad hoc: we shouldn't abandon the principle that animals form a natural kind (hence are animals throughout their careers) simply to avoid an inconvenient consequence of the claim that animals exist before conception. Further, we must deny that human animals were animals in their earliest stage even though they were living things composed of human cells-the sperm and the egg.

5 Note that ‘fetus’ refers to the animal which is at the fetal stage, not to the stage itself. ‘Fetus’ is like ‘child’ in ‘This child will inherit a fortune when she is thirty.’ The fetus can grow up, the fetal stage cannot.

6 Annis, David B. introduces the notion of ‘direct potentiality’ – in ‘Abortion and the Potentiality Principle,’ The Southern Journal of Philosophy 22 (1984) 155–63CrossRefGoogle Scholar. ‘Direct Potentiality’ is wholly a matter of causal strength for Annis; it does not involve an identity condition. A distinction closer to the one I want is implicit in Roger Wertheimer's observation that ‘ … people call the zygote a human life … because it and it alone can claim to be the beginning of the spatiotemporal-causal chain of the physical object that is a human body …’ (Wertheimer, Roger ‘Understanding the Abortion Argument,’ Philosophy and Public Affairs 1 [1971] 67–95Google Scholar, esp. 79).

7 A nature, we might say, is an inner principle a creature has from its beginning,which primarily determines a developmental path leading to the creature's adult stage and which also primarily determines the creature's fundamental characteristics. A genetic code is a universal because it can have instances, as in the case of identical twins. We might call an instance of a genetic code a genetic constitution. In higher animals we can identify a creature's nature with its genetic constitution.

8 A nature sufficient to be the primary determinant of a human developmental path is an instance of a human genetic code (what I called a genetic constitution in note 7). A genetic code is instantiated when the chromosomes of the sperm and the egg are united; a particular instance of a genetic code first exists at conception. Consequently the composite of the divided sperm and egg lacks a nature sufficient to be the primary determinant of a human developmental path.

9 Graeme Forbes observes that ‘the zygote ceases to exist upon replication’; he concludes that we contradict Leibnitz's Law if we identify the zygote with the resulting adult. (See Forbes, Graeme The Metaphysics of Modality [Oxford: Clarendon Press 1985]135Google Scholar.) This seems right: one cannot be two. Consequently the zygote lacks strong potentiality. It is only after the first cleavage, about twenty-four hours after conception in a human fetus, that there is an organism which develops without fissioning (of course, its cells fission). The conclusion that no cell the nature of which is to divide into duplicates can have strong potentiality entails that parthenogenesis, even if it became common, could not establish the strong potentiality of the unfertilized (or the self-fertilized) egg to become an adult human being.

10 Feinberg, Joel ‘The Rights of Animals and Unborn Generations,’ in Partridge, Ernest ed., Responsibilities to Future Generations (Buffalo, NY: Prometheus Books 1981) 145Google Scholar

11 The fetus needn't cease to exist if he veers from the developmental path determined by his nature; still that path has a special status. For each creature, there is a set of developmental paths increasingly diverging from the path determined by the creature's genetic constitution. The more paths diverge, the more they are determined by factors other than his genetic constitution: for example, environmental interference or genetic change. The more a path is determined by factors other than his genetic constitution, the less likely it is to be a path which guarantees identity (a path guarantees identity when a creature which follows that path must survive). Hence the path determined by the creature's genetic constitution is the paradigm of a path which guarantees identity.

12 Note that this account of the relation between nature, good, and identity does not appeal to teleology. The adult stage is not construed as a final cause or goal, for the sake of which the organism develops.

13 New Orleans Times-Picayune/States Item (Associated Press, Sept. 25, 1984), 23. The brain stem provides Andrew with motor functions like breathing and swallowing. I am supposing that Andrew is completely unconscious.

14 Andrew doesn't have a moral right to life, but we have good reasons to treat him as if he does. For if we allow parents, doctors, or the state to cause Andrew's death directly or by withholding medical care, we place all handicapped newborns in jeopardy. Indeed, they are already in jeopardy: mildly retarded newborns are sometimes starved to death in American hospitals when parents (often advised by doctors) refuse the routine surgery that will enable them to eat. Further, we ought to protect Andrew for the sake of those wishing to adopt him – twenty-four families tried to adopt Andrew and he was finally adopted by a nurse.

15 What do we owe an infant with a (supposed) correctible genetic defect that will stop him from growing up? I can only sketch an answer here. If the defect inhibits the operation of a complete genetic constitution, the infant has strong potentiality and we ought to correct it. If the infant's genetic constitution is incomplete (e.g., he will not develop a liver), but there is still a developmental path of which it is the primary determinant, namely, the path he will take if we plug the genetic gap, he has strong potentiality and we ought to plug it. If the code is so incomplete that it cannot be the primary determinant of a path, the infant Jacks strong potentiality. There may be a range of borderline cases.

16 Warren, Mary Anne ‘Do Potential Persons Have Rights?’ in Partridge, Ernest ed., Responsibilities to Future Generations (Buffalo, NY: Prometheus Books 1981) 264Google Scholar

17 Warren, 262. Also seep. 272, n.2. I am using ‘self-awareness’ as a place-marker for the conscious goods which characterize the lives of adult human beings. For Warren, self-awareness is one of a constellation of qualities (such as reason and communication), the absence of all of which precludes personhood.

18 Locke, John Essay Concerning Human Understanding, Ch. 27 in Perry, J. ed., Personal Identity (Berkeley, CA: University of California Press 1975) 39Google Scholar

19 Locke believes that identity conditions are determined by the idea we have of the entity in question (p. 37 in Perry); in particular, the idea of a person determines that personal identity consists in present consciousness and in memory. In fact, Locke's account of our idea of a person does not determine psychological identity conditions: nothing rules out the possibility that this thinking being is a man, that is, a living human animal, which can consider itself as itself in different times and places. Here the identity conditions for the sortal man do the work (person x at tl = person y at t10 if and only if x is the same man as y) and memory would not be a necessary condition for personal identity.

20 Consequently if that fetus had been aborted, I would have been aborted.

21 Suppose we identify a person with the stage of an animal during which it is self-aware (as opposed to the animal which is at that stage); then persons cannot exist before they are persons and they certainly were never fetuses. The trouble is that persons are substances (beings), not stages (temporal stretches) of substances. For example, persons are agents of actions and subjects of thoughts and feelings. A temporal stretch of an animal may contain actions and thoughts, but it is the animal, not the stage, that acts and feels. Further a whole person can exist at a point in time: I am all here now. But a whole stage cannot exist at a point in time: a temporal stretch cannot exist in its entirety at 10 AM.

22 I maintained earlier that a clonable cell ceases to exist upon fissioning, so it lacks strong potentiality. Consider the objection that the cell (C) constitutes a numerically distinct organism (O) which survives the demise of C and so has strong potentiality. My response is that if C constitutes O and C fissions, then O fissions, because C and O share all their non-modal non-temporal properties. Similarly, if the lump of bronze fissions, the statue fissions.

23 John Perry, book review of Williams, Bernard Problems of the Self: Philosophical Papers, 1956–1972Google Scholar, in The Journal of Philosophy 73 (1976) 421.

24 Williams, Bernard ‘The Self and the Future’ in Williams, Bernard Problems of the Self (Cambridge: Cambridge University Press 1973), 46–63CrossRefGoogle Scholar

25 This is why I could have been stolen from my incubator, raised by gypsies, and still been me, though that life would be wholly psychologically discontinuous from mine. The Psychological Criterion apparently entails that these lives would belong to different people, for no psychological event in either life is caused by an event in the other. (Supposing, on the other hand, I had been stolen at the age of ten: some psychological events in that life, e.g., memories, would be caused by events that are part of this one.) If we defend the Psychological Criterion by stipulating that psychologically discontinuous lives in different worlds belong to the same person if they belong to the same animal, why shouldn't psychologically discontinuous lives lived serially by the same animal (the brain zap) belong to the same person too? Or suppose I had merely been conceived a day later and that consequently no ensuing token mental event in my actual life. The Psychological Criterion entails that my body would belong to someone else, a man with my parents, my name, my friends, my profession, and so on.

26 There is considerable evidence that the same biological nature tends to create a marked psychological resemblance between the lives of different people who share it: studies of identical twins reared apart find striking correlations in brain wave activity, IQ, personality, political slant, and recreational and intellectual interests, compared to fraternal twins and the rest of the population. See Lykken, David T. ‘Research with Twins: The Concept of Emergenesis,’ Psychophysiology 19 (1982) 361–3CrossRefGoogle ScholarPubMed.

27 My thanks to The Canadian Journal of Philosophy and to my colleagues at The University of New Orleans for helpful comments on this paper.