Here are the key two paragraphs from Saletan's critique:

The pro-pros [i.e., people who are "pro-life" yet pro-stem-cell research] concede that if personhood begins at conception, it's immoral to destroy IVF embryos by taking cells from them. But personhood doesn't begin at conception, they say. It begins when the embryo is implanted in a womb. "To me, a frozen embryo is more akin to a frozen unfertilized egg or frozen sperm than to a fetus naturally developing in the body of a mother," Hatch wrote in a letter he forwarded to Bush last month. In an ABC interview, Hatch flatly declared, "Human life begins in the mother's womb, not in a petri dish or a refrigerator." At a recent hearing, [Sen. Gordon] Smith added, "If you have a stem cell in a petri dish and you keep it there for 50 years, you'll end up with a stem cell in a petri dish. And until you place that in a woman, you are not going to create a life."

On this theory, the value of human life, like the value of a house, is determined by location, location, location. Whether it's an egg or an embryo is less important than whether it's in a womb or a freezer. But location, unlike fertilization, is easily reversed. Take the embryo out of the woman, and it ceases to be a person. The pro-pro response to this objection is that you can't take the embryo out, since it's already a person. But if location, not fertilization, is what makes the embryo a person, then doesn't changing its location change its status? You don't have to kill it; you can just put it in a dish or a freezer. That's what happens to eggs in IVF, and the pro-pro senators have no problem with it. Is it OK to do this to an egg but not to an embryo? Why? The only difference is fertilization, which the pro-pros have dismissed as the standard of personhood. Having stipulated that a frozen embryo is more like a frozen egg than like an embryo in the womb, they have no grounds to complain. The adjective trumps the noun.

Here is the problem I see with Saletan's critique: So far as I know, Hatch never said or implied that "location, not fertilization, is what makes the embryo a person." (His "To me, a frozen embryo …" sentence doesn't logically imply this.) Rather, he said that location plus fertilization is what makes the embryo a person. In other words, a) neither location in the womb nor fertilization is by itself a sufficient condition for personhood; b) each by itself is a necessary condition; c) when both occur they together constitute a sufficient condition. So far as I can tell, this is a perfectly coherent position, devoid of internal contradictions. It may be that Saletan could trace out the logical implications of this position in ways that would change my mind. But he'll have to start afresh. By mischaracterizing Hatch's position at the outset, he has (IMHO) undermined the rest of his argument.

Thus (in the second paragraph above), he goes on to suggest that Hatch can't logically condone the removal of an egg from a woman's womb for IVF while opposing the removal of an embryo from a woman's womb for research because Hatch has "dismissed [fertilization] as the standard of personhood." But in fact what Hatch has done is make both fertilization and location in the womb the collective standard for personhood. In the case of an egg, the standard hasn't been met, so you don't have a person, but in the case of an embryo in the womb, the standard has been met, so you do have a person. Again, this strikes me as an entirely coherent position—and I render this judgment as someone who, so far as I can recall, has never before written anything even remotely favorable about Orrin Hatch.

Other parts of Saletan's analysis I find persuasive. For example (see item No. 4 in his piece), he notes that when people such as Hatch and Smith use the logic I used in my piece to characterize embryonic stem-cell research as "pro-life," they are using a utilitarian morality that they and other pro-lifers reject in other contexts. But this is a separate matter from the argument of Hatch's that I focus on in my piece—that the nonutilitarian philosophical framework underpinning the traditional pro-life position doesn't logically entail opposition to embryonic stem-cell research.