Slate’s William Saletan has a thoughtful column today comparing the rhetoric on stem cells to the rhetoric on torture.

You don’t have to equate embryos with full-grown human beings—I don’t—to appreciate the danger of exploiting them. Embryos are the beginnings of people. They’re not parts of people. They’re the whole thing, in very early form. Harvesting them, whether for research or medicine, is different from harvesting other kinds of cells. It’s the difference between using an object and using a subject. How long can we grow this subject before dismembering it to get useful cells? How far should we strip-mine humanity in order to save it?

If you have trouble taking this question seriously—if you think it’s just the hypersensitivity of fetus-lovers—try shifting the context from stem cells to torture. There, the question is: How much ruthless violence should we use to defeat ruthless violence? The paradox and the dilemma are easy to recognize. Creating and destroying embryos to save lives presents a similar, though not equal, dilemma.

This is a difficult moral dilemma, he emphasizes — not a case of science vs. ideology. If we don’t recognize the dilemma and wrestle with it, our ethical lines will slide. His closing line:

The stem-cell fight wasn’t a fight between ideology and science. It was a fight between 5-day-olds and 50-year-olds. The 50-year-olds won. The question now is what to do with our 5-day-olds, our 5-week-olds, and our increasingly useful parts.