William Hurlbut seems to be the only person in this debate who has figured out that the Catholic fixation on the technical definition of a human embryo, which stem-cell researchers regard as a roadblock, actually presents an opportunity. [...]

Hurlbut has modeled his recipe on "aberrant products of fertilization" and teratomas, which, he explains, are "germ cell tumors that generate all three primary embryonic germ layers as well as more advanced cells and tissues, including partial limb and organ primordia." Limb and organ primordia? Yep, that's what's on the screen: a ball of tissue, grown inside some poor creature, full of bits and pieces of what would have been a body. Another slide shows an X-ray image of somebody's back. To the left of the spine, you can see a cluster of white spots that look like teeth. And that's exactly what they are, all dressed up and no place to chomp. You wanted disorganized development? You got it. [...]

Hurlbut replies, coldly but correctly, that according to the technical definition favored by opponents of stem-cell research, the thing can't die because it was never alive. Michael Gazzaniga, the council's most liberal member, calls Hurlbut's strategy a perversion of science. Instead of tinkering with language to fit biology, he observes, Hurlbut is tinkering with biology to fit language.

I strongly recommend that you not type the word "teratoma" into Google Image Search.