1 Quoted in Charles Gardner, ‘Is an Embryo a Person?’ The Nation (November 13, 1989),557.

2 Singer, Peter & Dawson, Karen ‘IVF Technology and the Argument from Potential,’ Philosophy and Public Affairs 17 (1988), 89Google Scholar

3 Canadian Journal of Philosophy 17 (1987) 815-30. Parenthetical page numbers are to this article.

4 What is at issue is whether the objective, observer-independent character of the embryo grounds a claim to protection. It is undeniable that the potentiality of the embryo to be an infant, and of an infant to be an adult, matters very much to prospective parents. Stone’s account aims to show that to deliberately throw away a glass dish with fertilized eggs in it is a harm comparable to killing an infant, and that independently of whether anyone cares about a given embryo it merits protection because of the sort of entity that it is.

5 Stone implies that appeal to a special developmental obligation is the only plausible way to ground our concern for infants. However, an ‘actualist’ can account for a right of babies not to be painlessly killed by appeal to the properties and capacities that even a young infant already has.

6 We have obligations to creatures in virtue of their strong potentiality but not in virtue of their weak potentiality. He summarizes his argument this way: ‘As the fetus is identical to the adult animal she produces and identical animals share their properties, the fetus will think, feel, and be self-aware if she develops normally.If we kill the fetus we deprive her of a welfare she would otherwise have realized for herself. The sperm and the egg, on the other hand, can never have these properties even though they can produce something which can.If we kill them there is no good of which they are deprived’ (823).

7 See Grobstein, Clifford From Chance to Purpose: An Appraisal of External Human Fertilization (Reading, MA: Addison-Wesley 1981), 41-2.Google Scholar

8 In fairness to Stone, I note that in places he offers a weaker claim. He says in a footnote, ‘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,’ and ‘the path determined by the creature’s genetic constitution is the paradigm of a path which guarantees identity’ (821, n. 11). This won’t do at all. If the embryo can develop into various different creatures which will be identical to it, then, if these creatures differ from each other in important ways, potentialism collapses. Presumably Stone would not wish to grant that identity is even possibly preserved if the paths differ as much as they do in the examples I discuss below.

9 Several of the more salient are usefully summarized in George Myro, 1dentity and Time’ in Grandy, Richard E. and Winner, Richard eds., Philosophical Grounds for Rationality: Intentions, Categories and Ends (Oxford: Clarendon Press 1986) 383-409.Google Scholar See also Noonan, Harold Objects and Identity: An Examination of the Relative Identity Thesis and its Consequences (The Hague: Nijhoff Publishers 1980)CrossRefGoogle Scholar; Hirsch, Eli The Concept of Identity (Oxford: Oxford University Press 1982)Google Scholar; and Brennan, Andrew Conditions of Identity: A Study of Identity and Survival (Oxford: Clarendon Press 1988).Google Scholar

10 Even worse, there are alternatives to the potentialist assumption of identity between embryo and adult. E.g., on the constitution view one might hold that the relation of the embryo to the baby is analogous to the relation of a lump of wax to a statue that it is formed into. The wax constitutes the statue but is not identical to it. Although a developing embryo is enormously more complicated than a lump of matter, it could be viewed as being constituted by material that will develop into the material out of which a child is constituted. Just as the wax only becomes (in the constitution sense of ‘becomes’;) a statue after it is formed into a particular shape, so a developing prenatal organism only becomes a baby after its organic matter and structures are formed into a particular functioning organism with certain phenotypic characteristics (e.g., sensation). For example, in the development of a frog, there is first a fertilized egg, then a tadpole with gills and a tail fin, then a frog with lungs and legs. The frog and the tadpole are, in this way of thinking, analogous to two sculptures made out of the same lump of wax, and like two different sculptures are not themselves identical to each other. This account, if defensible, shows that Stone’s assumption of identity is not logically necessary.

Stone is aware of this alternative. He devotes section m of his paper to trying to block the person-comes-into-existence move. But his treatment is not directed at the (biologically) general form of the constitution position. Moreover, he continues to assume an identity of the adult animal (on the hypothesis he is arguing against, not assumed to be the person) and the embryo in his counter-argument, an identity that would be denied by the constitution position.

11 See Brody, Baruch Identity and Essence (Princeton: Princeton University Press 1980)CrossRefGoogle Scholar for dogs-into-blobs examples.

12 There is an additional problem with the ‘one cannot be two’ slogan that Stone uses to dispense with awkward but real possibilities like a cloned cell and an ova that is about to divide through parthenogenesis. This slogan invites the ‘Placenta objection’: on the grounds that ‘one cannot be two,’ mustn’t we reject the identity of the fetus with that of the embryo before it separates into the embryo proper (fetus) and the extraembryonic membranes?

13 Strictly this may have to be reduced to an ‘only if’ to deal with puzzle cases from the personal identity literature, but for simplicity I will keep the formulations of identity conditions throughout ‘iff.’ This does not affect my argument.

14 I am assuming in all formulations of identity conditions that twinning or splitting does not occur.

15 Baskin, Yvonne The Gene Doctors: Medical Genetics at the Frontier (New York: Morrow 1984), 190-1Google Scholar

16 David Lygre, Life Manipulation (New York: Walker 1979), 28

17 C.f. Edlin, Gordon Genetic Principles: Human and Social Consequences (Portola, CA: Jones and Bartlet 1982), 329-30Google Scholar; also Baskin, 177-84.

18 Science Impact Letter (May 1988), 1

19 Many variables have already been identified that can alter the expression of genes in plant cells, e.g., water stress, heat shock, pathogens, heavy metals, anaerobiosis, etc. C.f. Matters, G.L. and Scandalios, J.G. ‘Changes in Plant Gene Expression During Stress,’ Developmental Genetics 7 (1986) 165-75.CrossRefGoogle ScholarPubMed Alterations in the development of Drosophilia due to heat shock on the embryo at certain stages have been demonstrated. SeeS. Ebertein, ‘Stage Specific Embryonic Defects Following Shock, Heat in Drosophilia,’ Developmental Genetics 6 (1986) 179-97.Google Scholar

20 Stone appears to have elements of both accounts, (M) and (ND), of a nature.

21 Baskin, 240

22 The last clause is necessary to rule out magic-wand examples such as those that might transform a kitten into a puppy; these would otherwise be counter-examples if we interpret ‘developmental paths’ very loosely.

23 Hirsch, 37

24 Hirsch, 36

25 Wiggins, David Sameness and Substance (Oxford: Blackwell 1980), 24-5Google Scholar

26 See Hirsch, 56.

27 Wiggins, 63

28 As a bare formal possibility one could wonder about a disjunction of these two criteria. Against this I would suggest (a) Why would the disjunction be necessary to preserve identity when neither disjunct is? We would need an elaborate explanation. (b) This is supposed to be an explanation of a creature’s nature. A disjunctive nature seems unconvincing.

29 If we were forced to say that the embryo has a probabilistic nature, wouldn’t this by itself undermine potentialism?

30 Singer and Dawson, 100

31 Nor does evolution privilege ‘normal’ outcomes in the way required by potentialism. ‘Evolution’ is merely the name of a set of explanatory principles that account for the historical development of species; it doesn’t specify a force that intends an end or prevents a change in the characteristics of species or individuals.

32 Gareth Matthews has suggested (in correspondence) that we could define normal development as that development that tends to be species preserving. This may be a useful definition of normal development, but it would be too restrictive as a principle of identity preservation in (NI). Not only would (NI) under that definition beg the question against the sorts of counter-examples I have offered, but it would rule out as identity preserving such obvious examples as organisms born with serious birth defects, mutations leading to new species and sterile hybrids such as mules.

33 I wish to thank Marc Bekoff, Dale Jamieson, Gareth Matthews, and Christopher Shields, as well as an anonymous editor and an anonymous referee for the Canadian Journal of Philosophy, for helpful comments on earlier versions of this paper.