If what I wrote in Part 2 is correct, certain pro-life arguments are flawed to the extent they rely on living beings having one definite "substance kind." I agreed that I am a human organism – just as human embryos are — but it's also true that I am a mammal and that I am a heterogametic being. The first category applies to whales and the second fails to apply to about half of all human embryos.
Still, these are all categories for organisms. The authors of Embryo spend considerable time arguing that 'I' statements refer to the organisms we are (however we might characterize such organisms). "I composed a haiku" must be saying that a particular organism composed a haiku. And since this particular organism began to exist as a single cell zygote, any use of 'I' is mistaken if it does not refer to an entity which began to exist at that time.
Even if adults and embryos don't all share one (and only one) substance kind, perhaps every adult shares one (and only one) identity with a past embryo.
This is the point made in the opening of Embryo, which describes an infant born in 1997 as a survivor of the 1995 hurricane Katrina; he was a frozen embryo at the time, you see. I won't dispute that Noah — as he was named — shares an identity with that embryo rescued from a flooded hospital. It's true that Noah was rescued as an embryo. However, it's also true that he was not.
Oh. I must be one of those crazed relativists, right? In some areas I am a relativist, but I suggest reserving 'crazed' for the ones who endorse contradictory propositions. I'm only claiming that the two boldface statements above which appear contradictory aren't necessarily in conflict because we can and often do mean different things by 'I' language (and 'he' language in this case). Furthermore, such variations may interfere with clear communication, but aren't otherwise a mistake, since personal identity is a conceptual chimera rather than a reality.
Consider this snag:
It is necessary to add the qualification "the vast majority of us," because there are exceptions to this claim about the beginning point of human beings. For identical twins do not come into existence at fertilization. At least one twin comes to be at a later point when the embryo divides—probably because of some extrinsically caused disruption—into two genetically identical human beings. What has happened to the early embryo? Some think that the early embryo is identical to one of the subsequent twins; it is as if a new embryo has "budded" off from the first. Others think that the first embryo ceases to be, and two new embryos take its place.1Well, which is it? Are the authors waiting on a biological fact that embryologists just aren't sure about yet? They can't be reserving judgment on account of not knowing whether the first embryo's soul (if it had one) is attached to one, both, or neither twin; they've already sworn off dualism! Might I suggest it's up to us to arbitrarily decide to count the original embryo as identical to one, both, or neither of the twins?
Same goes for science fiction scenarios about teleportation copies and personality reprogramming.
Or, better, perhaps we should realize that such odd cases reveal seams in the patchwork of personal identity. There's no simple, objective fact of the matter whether an original embryo survives twinning. Why, then, would the situation be different if no twinning occurs?
Without a strongly realist view of personal identity, 'I' language is set free to apply to the different ways we think of identity. Would I survive a personality reprogramming? A permanent removal of conscious awareness? A teleportation? A bodily resurrection? A religious conversion? A mental state upload to a computer? A piecemeal physical replacement? A brain (or body) transplant? A millennium in cryostasis?
We can get different answers depending on which aspect of personal identity we're asking about.
Back to Noah. How can I say it's (also) true that he wasn't rescued as an embryo? Because here I'm using a 'he' which indicates Noah's conscious lifetime, so to speak. This isn't some other substance I'm claiming Noah "really is" rather than a human organism (or vertebrate organism, or male organism).2 I am merely using an aspect of personal identity focused on first-person experience, not biological life.
This view might be called linguistic dualism in contrast to metaphysical dualism, but 'I' language pluralism would be more accurate. It accommodates 'I' language which focuses on bodily action, language which combines body and mind, and also allows for language limited to a concern for mental attributes. Metaphysical dualism may turn out to be an illusion, but even then we may want to retain a way of speaking about ourselves that doesn't begin and end with our organism.
1. George, R.P., Tollefsen, C. (2008). Embryo: A defense of human life. New York: Doubleday. p 55.
2. As metaphysical dualism is described on p. 61.