If you believe that human beings exist from the moment a zygote comes into being, there are almost no environments more dangerous for humans than inside their own mother.

Well, sure – but if you believe that human beings exist from the moment a zygote comes into being, you could just as easily argue that the safest environment for a human being, at that stage of its development, is inside its own mother. Yes, it’s still a pretty dangerous place – but so was the environment outside the mother’s womb, until the last hundred years or so. A kid born in Chicago in 1870, for instance, had a fifty percent chance of reaching the age of five. But that didn’t make him any less of a human being.

And it’s not quite true that, as Andrew puts it, “comparing the scale of what humans do to the unborn with what nature does is like comparing a high tide with a tsunami.” It’s more like comparing a middling tsunami to a major one. There are about 4 million births a year in the United States, and if we suppose that only a third of zygotes make it through to birth, that means that about eight million human lives perish naturally in utero. This is obviously a lot more than the between 1 and 1.5 million abortions that have taken place every year since the mid-1970s – but not so much more that the latter statistic fades into insignificance.

And even if it did, so what? “Nature” kills everyone, eventually. The death rate for people in the stage of development we call the eighth decade of life is probably around eighty percent or so. That doesn’t make it less of a crime if someone bumps my grandmother off. We don’t have laws against murder because we want to lower the death rate to zero – we have laws against murder because we accept that 1) everyone dies, but 2) it’s not okay to kill them.

Obviously, nature’s waste is a strong intuitive argument against the pro-life position – i.e., if zygotes and embryos perish in such great numbers, how can they be that important? If we don’t know these lives exist, and don’t grieve when they’re accidentally snuffed out, why isn’t okay to kill them? But I don’t think it makes for a very strong logical argument. The crux of the abortion debate is whether there ought to be a legal distinction between human lives (which zygotes and embryos and fetuses obviously are) and human persons – defined variously by brain activity, ability to feel pain, level of self-awareness, possession of language, ability to survive independent of their mother’s body, or what-have-you. And intuitions aside, I don’t think even the most ardent pro-choicer wants to start defining “personhood” based on survival rates. You won’t like where it takes you.

– posted by Ross

UPDATE: I simply want to echo every single point of Ross’. There’s a distinction between wilfull taking of human life and nature’s toll, beyond human control. The argument about zygotes does not logically alter the absolutist pro-life case, but it does, I think, provide context for an intuitive sense (echoed by Aquinas) that it’s too extreme a view. The tsunami-tide metaphor may be excessive. But the ratio of natural abortions to procured ones is still around 8:1. As for “personhood,” Ross is right again: that’s a separate question. I deal with all this in the book. The blog post was designed to nail down a fact.

– posted by Andrew.