It’s not entirely a slippery-slope argument if you buy that “week-old blastocysts” are human beings, however early on in their lives. They deserve protection as such. Supreme Court decisions aside, the law gives cover for that; not to be positively grade-school about this, but really ABC civil/social agreements like the Declaration of Independence & Constitution, and, forgive me, the Universal Declaration on Human Rights include this principle. That’s not exactly a “single, precise, all-encompassing moral dogma” being imposed on a people clamoring for a form of research that hasn’t even been subject to an intelligent national debate. (When it comes to imposing my absolutist RTL will on the country, I wouldn’t hold too strongly to the argument that Americans are overwhelmingly agreed on the “week-old blastocyst.” And even if we were, again, it’s a fundamental that deserves the least amount of fudge and compromise as is possible and plausible. )

I suppose the rest of my argument is a slippery-slope argument, but as a matter of principle I’m not opposed to making slippery-slope arguments when you’re on an obvious slide.

Just quickly (deadlines, deadlines): As for your voting comparison–I guess I just don’t see the voting age to be as fundamental as the right to life, and I can’t see the hypothetical pro-nine-year-olds voting advocates having too much of a compelling case.

Back to the slide, I go to Ponnuru again, because he’s already written it. This time in NRODT (“Cells, Fetuses, and Logic,” July 23, 2001):

A pro-life position not rooted in logic ends up having the same line- drawing problem. When do pro-life supporters of stem-cell research believe life begins? They would seem to believe that a clump of matter that is not a person somehow becomes inhabited by a person as it develops. Rather than defend this theoretical disaster bordering on superstition, some of these pro-lifers have resorted to the name games that pro-choicers have used in the past: Blastocysts aren’t embryos, embryos that have not been implanted are pre-embryos, etc. But none of these nominal distinctions-nor the biological distinctions they denote- mark a point of moral distinction.
[Robert] Bartley describes himself as a member of the “mushy middle” on abortion as though it were good in itself not to draw principled distinctions. He opposes partial-birth abortion because it is ugly, supports stem- cell research because nobody grieves for blastocysts, seeks a middle ground because the extremists are off-putting: a clump of positions united only by sensibility.
The trouble with this middle ground is that, in addition to giving up territory that should be defended, it is itself indefensible territory. Slippery slopes are slippery because the logic that starts you down them will lead you further down. During the stem-cell debate, people have said that it’s okay to use embryos for research because we already “discard” plenty of embryos as a byproduct of in vitro fertilization; they could with equal validity say that we should allow research on five-month-old fetuses because we allow them to be aborted. Judges have said that we have to allow partial-birth abortion, or even euthanasia, because we allow abortion. The Washington Post says that the logic of abortion rights does not permit the law to charge people with murder when they kill an unborn child in the course of an assault on a pregnant woman, even if the woman considers it murder.
Slippery-slope arguments rarely succeed because people discount the possibility of remote future horrors; they think they will be able to stop the slide. But horrors can get less horrible as the future becomes less remote. People adjust their sensibilities. In 1973, not even pro- abortion lawyers were challenging Texas’s law against partial-birth abortion. Back then, embryo-killing research would have seemed monstrous. I have read the argument (in Reason, the libertarian magazine, as it happens) that people predicted all kinds of dire consequences from in vitro fertilization that did not happen, so why not allow cloning? One of the dire consequences of in vitro fertilization, however, is precisely that we are debating cloning now.
A common trope of the press coverage of the stem-cell conflict-which reeks of weariness at the continued existence of pro-lifers-is that it’s a shame this “scientific issue” has gotten caught up in the “politics” of abortion. But it is caught up in the issue because the premises of the arguments are the same: Either conception results in a new human being deserving of legal protection or it doesn’t. No amount of sophisticated hairsplitting over bioethics is going to work if it ignores that awkward, obvious question.