Animals: fuck those guys (a post that's actually about abortion)
Or, in the words of Jeff Mirus, the problem with people comparing their gut feelings about a child to their gut feelings about a dog is "that the dog has no value but that their minds" whereas children (read: fetuses) have some other kind of value. See, for Mirus, the world "cannot be interpreted morally without a great respect for the concept of personhood." Having this respect in hand, he says, we will understand - and I'm sure you already know where this is going - "that all non-personal being is [sic] at man's disposal" in precisely the same sense that "no personal being," including a fetus, "is at man’s disposal." How reasonable this all is will depend on what Mirus means by "personal being."
Thankfully, he actually gives us this definition: "every person has both intellect and will and so is at least potentially capable of entering into relationships of love." As for "relationships of love," those happen through "an act of the will based on a proper intellectual valuation of the other, a valuation through which the intellect instructs us to love, that is, to will the other's good." Got it? People have intellect and will and are capable of properly intellectually evaluating others and choosing to act in their benefit. If any of this sounds familiar, you've been paying attention: we've been here before.
When I went through this whole thing with Joel last month, I was never able to get him to see the whole picture at once. At first he used the definition that "any human being...is one that has 'potential for growth and full realization.' Potential for growth is one of the necessary characteristics in defining a thing as living and human beings by definition are animals capable of full realization." This seems to be the direction Mirus is going: work with established scientific terms ("intellect," "animal," "growth") and use their common meaning to show that fetuses are just the same as full-grown humans. But this leads to problems, especially for religious frameworks like the one Mirus explicitly operates in. For one thing, not all human-patterned DNA physically has the potential to grow and develop - some will die in vitro, some will live but fail to develop higher brain functions, etc. Even worse, some humans who actually do have will and intellect and all that jazz will eventually lose those capacities permanently, at which point Mirus is bound to say that they're no longer people. Since he refuses to do this - and, more broadly, since both he and Joel refuse to say that fetuses without the physical capacity for development aren't people - this route won't work for them.
Going for something more metaphysical, then, seems to be the right response. This can be done in one of two ways: either through a religious perspective or not. Joel chooses the latter, and this option is also open to Mirus (though he'd never take it). The most famous account of this can be found in Aristotle's De Anima, and that's precisely where Joel looks: according to Aristotle, he says, "there is a particular kind of living thing that has the capacity for reason, namely human beings. Given that reason is such that it cannot be attributed to matter per se...he attributes it to the immaterial soul. Now if the soul as such that it makes the particular living thing be what it is (a human, a monkey, a giraffe, etc.) and is also the principle of life, then any human living thing posesses a rational soul." In cases where the human doesn't actually develop or even cannot actually develop rationality (or, for Mirus, intellect and will), the differences are "purely accidental" - that is, they don't make a difference one way or the other about whether the thing really is a person or not. (Here I leave aside the issue of whether Joel misreads Aristotle, which I think he does. Assume for the sake of argument that he doesn't.) This saves them from admitting that it's okay to kill e.g. really senile people, but it has two very awkward consequences, one ontological and the other epistemological.
First and foremost, this will be bad news for people with conjoined twins. Even in the case where the conjoined twin is just limbs, we'd have to give that entity the same rights we give a full person: after all, the fact that it can't possibly develop rationality or intellect (because it can't even develop a head or a brain) is just an accident, not something that affects what they really are. Similarly for other biological conditions wherein a human fetus or blastocyst is physically restricted from ever reaching full human development, we would be bound to consider them full people and treat them as such. Joel denies this, though, and I bet Mirus would, too. From another point of view, we'd also have to be much more careful with the dead: since physical death is just an accidental state (i.e., not something that affects the metaphysical substance), we'd have to totally overhaul our practices concerning the dead. Especially since we still can't say for sure when a person is biologically dead for good, we would have to begin behaving towards the dead just like we do towards the living (at least, for some significant interval). This may not seem so unreasonable, but consider also that we can keep bodies alive for a very, very long time even without brain stem activity if we try hard enough: since this, too, is just an accident according to this argument, we'd have to treat even decapitated bodies as though they were just fine. Again, I don't think this is something that Joel or Mirus wants to adopt, so I have no choice but to conclude that the secular-soul strategy unavailable to them both.
Finally, Mirus could retreat to a religious (in this case, Christian) conception of the soul. (Joel could've, too, if he hadn't committed himself to making a universally accessible argument.) The biggest problem here - besides, of course, the total lack of evidence and other various problems associated with religion in general - is that Mirus must maintain a certain exclusivity. He has to say, in other words, that only humans have rational souls - or, in his words, that "[n]either a dog, nor a dolphin, nor a chimpanzee, nor any other embodied being besides man is capable of" love (i.e., properly evaluating others and acting for their benefit as a result of this evaluation). As well as this matches up with his tradition, this is a view that can no longer be sustained in the face of the facts. When he claims that animals "give no evidence either of intellectual analysis or of moral judgment," Mirus is just plain full of shit. It seems, then, like the only way out for Mirus and Joel would be to postulate something like this from the start:
(*) By definition, a person (or "living being worthy of moral respect") is either a living human fetus at any stage of development or a living human at any post-fetal stage of development, so long as it has a head and some part of a brain.
There is no obvious set of axioms that leads to this definition, nor can it be easily defended from criticism - in fact, it looks like exactly what it is: a cobbled-together set of conditions with no connection to the actual world. But it's what Mirus and Joel would have to use if they even wanted to start their argument against abortion (and, in Mirus's case, animal rights). And I do mean start: if that definition holds, we'd be free to analyze fetuses as though they were regular ol' people, which means holding them responsible for their actions. Recall, for instance, what Mirus said about humans: no personal being is at the disposal of any human. Very well: then no woman is at the disposal of any fetus! Even if we ignore all of the inconsistencies and factual errors in their respective cases, then, neither Mirus nor Joel has even come close to giving a compelling reason why abortion is wrong.
The unspoken implication here - and the real force behind the argument - is that abortion treats humans (i.e., fetuses) like animals (i.e., non-human animals), and this line of thought certainly resonates powerfully with the unconscious hierarchy that many of us work with on a daily basis. But until we get workable definitions of the relevant terms involved, this will never be anything more than suggestion and innuendo, totally unsuitable for philosophical discourse.
