¹ See also E. Kingma, ‘Were You a Part of Your Mother? The Metaphysics of Pregnancy’, Mind (forthcoming).

² See e.g. Anscombe, G.E.M., ‘Were You a Zygote?’, Royal Institute of Philosophy Lecture Series 18 (1984): 111–115Google Scholar; Oderberg, David S., ‘The Metaphysical Status of the Embryo: Some Arguments Revisited’, Journal of Applied Philosophy 25 (2008): 263–276CrossRefGoogle Scholar; Olson, E., The Human Animal: Personal Identity Without Psychology (Oxford University Press, 1997)Google Scholar; McMahan, J., The Ethics of Killing: Problems at the Margins of Life (Oxford University Press, 2002)CrossRefGoogle Scholar.

³ To be precise: Placental reproduction. Placentals are the subset of mammals that have prolonged placental pregnancies, to be contrasted with marsupials (e.g. wombats) and monotremes (e.g. platypus). I use mammal to mean ‘placental mammal’ throughout the paper.

⁴ Note that there although embryogenesis is similar and remarkably robust amongst placental mammals (indeed amongst all vertebrates), there are relevant differences. Humans mostly have singleton pregnancies, for example, whereas many other mammals do not. Placental physiology also shows considerable variation. If this affects my arguments then my claims are restricted to human mammals and other mammals with sufficiently similar placental physiology.

⁵ E. Kingma, ‘Were You a Part of Your Mother? The Metaphysics of Pregnancy’.

⁶ Smith, Barry & Brogaard, Berit, ‘Sixteen Days’, Journal of Medicine and Philosophy 28 (2003): 45–78CrossRefGoogle ScholarPubMed.

⁷ Ibid.

⁸ I do not want to suggest that ‘foster’ is a morally or even metaphysically unified category; there are many relevant and interesting differences between zygotes, term-fetuses and the many stages in between. But for the purposes of this paper, i.e. investigating the relationship between the foster and gravida during pregnancy, they can be collapsed into one category (though with a possible exception for pre-implantation – see note 18).

⁹ Barry Smith & Berit Brogaard ‘Sixteen Days’. See listings on http://ontology.buffalo.edu/smith/

¹⁰ Barry Smith & Berit Brogaard, ‘Sixteen Days’, 47.

¹¹ In the sense that they do not require other entities as their ‘bearers’ or ‘carriers’, such as a smile which needs a face to bear it.

¹² This criterion bears a strong resemblance to traditional ideas of homeostasis.

¹³ Smith & Brogaard, ‘Sixteen Days’, 51.

¹⁴ Ibid., 62

¹⁵ Oderberg argues, I think correctly, that differentiation and causal unity actually precede gastrulation. I add support to this point at the end of section four (David S. Oderberg, ‘The Metaphysical Status of the Embryo: Some Arguments Revisited’).

¹⁶ Smith & Brogaard ‘Sixteen Days’, 65.

¹⁷ Ibid., 70. See also Smith, Barry & Varzi, A., ‘The Niche’, Nous 33 (1999): 198–222CrossRefGoogle Scholar.

¹⁸ After implantation, that is. Before implantation this is a different matter, as IVF illustrates. If and how the arguments apply prior to implantation will have to be addressed another time.

¹⁹ Oderberg notes that in discussions of the metaphysical status of fetuses it is conventional to take the future baby view of the foster (he calls it the fetus proper). But, he says, there is nothing inconsistent about taking something like the chorionic content or baby-with-placenta view (‘The Metaphysical Status of the Embryo: Some Arguments Revisited’).

²⁰ Barry Smith & Berit , ‘Sixteen Days’, 72. See also Smith, Barry & Varzi, A., ‘Fiat and Bona Fide Boundaries’, Philosophy and Phenomenological Research 60 (2000): 401–420CrossRefGoogle Scholar.

²¹ Smith and Brogaard, ‘Sixteen Days’, 73.

²² For a more detailed version of this argument, see Kingma, ‘Nine Months’, Journal of Medicine and Philosophy (Revise and Resubmit).

²³ E. Kingma, ‘Were You a Part of Your Mother? The Metaphysics of Pregnancy’.

²⁴ It is less controversial that organisms can be part of other organisms of a different kind Wilson, Robert A. & Barker, Matthew, ‘The Biological Notion of Individual’, The Stanford Encyclopedia of Philosophy (Spring 2014 Edition), Zalta, Edward N. (ed.)Google Scholar, URL = <http://plato.stanford.edu/archives/spr2014/entries/biology-individual/>.

²⁵ See e.g. Smith & Brogaard, ‘Sixteen Months’, 47, criterion 4: ‘Substances are distinguished, […] from the undetached parts of substances. The latter can become substances, but only through becoming detached.’ This they reassert e.g. (53) ‘We might attach a new tail to a tailless cat. Before the attachment, cat and tail are separate substances. As a result of the attachment, what had been a separate substance is now a part of the cat.’

²⁶ And this is precisely the attraction of having the concept of an organism. In other parts of biology, such as plant biology, the concept becomes much less useful as the distinction between different organisms becomes exceedingly fuzzy. In fact the very question whether ‘organism’ is a useful biological category is a live one (Haber, Matt H., ‘Colonies are Individuals: Revisiting the Superorganism Revival’, in Bouchard, F. and Huneman, P. (eds), From Groups to Individuals: Evolution and Emerging Individuality, The Vienna Series in Theoretical Biology (Cambridge, MA: MIT Press, 2013)Google Scholar). If the concept is to make sense anywhere however, the best candidates are mammals and other complex, multicellular animals such as birds, reptiles and fish.

²⁷ Babies, for example, breathe, scream, oxygenate their blood in their lungs, have close to 100% oxygen tension in their arteries and use their heart as a dual-pump maintaining separated somatic and pulmonary circulations. They also stop at the umbilicus. Fosters, by contrast, use their heart as a single pump, have much lower oxygen tension in their arteries (and, as a consequence, look more purple than red), and may have an entire extra organ that the baby lacks: the placenta.

²⁸ Note that the numerical identity block only applies to the foster; this is not, or at least not obviously, a problem for the gravida. Organisms survive changes including the loss and gain of bits all the time, therefore that the gravida loses parts – kidneys, ova, hair, menstrual discharge and fosters – is not itself an immediate threat to her survival.

²⁹ See e.g. Olson, E., The Human Animal: Personal Identity Without Psychology (Oxford University Press, 1997)Google Scholar.

³⁰ See e.g. Olson, E., What Are We? A Study in Personal Ontology (Oxford University Press, 2007)CrossRefGoogle Scholar.

³¹ See e.g. Koslicki, Kathrin, ‘Substance, Independence, and Unity’, in Feser, E. (ed.), Aristotle on Mind and Metaphysics (Palgrave MacMillan, 2013), 169–195CrossRefGoogle Scholar; Toner, Patrick, ‘Independence Accounts of Substance and Substantial Parts’, Philosophical Studies 155 (2010): 37–34CrossRefGoogle Scholar.

³² Smith and Brogaard's original justification for adopting the ‘no-niches’ condition on parthood was the need to exclude organs from being human organisms. (‘For consider John's heart. This is a substance, and it is a relatively isolated causal system; it is non-divisible; and it is a product of human reproduction; yet it is not itself a human being because it is not a maximal entity satisfying these conditions: it belongs as proper part to John's organism as a whole.’ ‘Sixteen Months’, 68). That is surprising because on their own criteria, involving complete external boundaries, human organs were never candidates for being either substances or organisms in the first place. What this may indicate is that Smith and Brogaard had a more liberal interpretation of external boundaries and substances in mind all along – though I am not sure what that interpretation would amount to.

³³ Wiggins, David, Sameness and Substance (Cambridge MA: Harvard University Press, 1980), 73Google Scholar.

³⁴ In the sense relevant here – as not requiring something else to instantiate its existence as a smile is instantiated by a face.

³⁵ E.g. the kidney has membranes that serve as a barrier to the peritoneal cavity; the brain has membranes that protect it from impact as well as from various chemicals in the blood that cannot traverse this membrane, and so on. Smith & Brogaard (‘Sixteen Months’, 52): ‘The heart and lungs, too, are separated from each other by appropriately constructed membranes (pericardium, pleura), which shield the processes occurring within them from outside influences.’

³⁶ Parts of kidneys and other organs, for example, locally regulate vasodilation and vasoconstriction. Human testes have their own temperature regulation mechanism, keeping the sperm at a considerably lower temperature than the rest of the body.

³⁷ Organs also have local mechanisms for replacing cells, membranes and other damage – and even considerable abilities of regeneration (e.g. liver).

³⁸ Does it mean ‘uninterfered with by humans?’ (in which case, what about IVF? And what about the fact that all human conceptions involves two adult humans ‘interfering’ with each other?); does it mean ‘without technology’? Does it mean ‘statistically normal’? Etc.

³⁹ Smith & Brogaard, ‘Sixteen Months’.

⁴⁰ Oderberg makes a similar point (in ‘The Metaphysical Status of the Embryo: Some Arguments Revisited’).

⁴¹ See e.g. Anscombe, ‘Were You a Zygote?’; Smith & Brogaard ‘Sixteen Months’; Harris, J., Clones, Genes & Immortality (Oxford University Press, 1998)Google Scholar.

⁴² Kingma, ‘Were You a Part of Your Mother? The Metaphysics of Pregnancy’.