What does it mean to respect human life? That question is at the heart of the current debate swirling around research into human embryonic stem cells, and answering it is no easy task. George W. Bush's solution is a policy he announced in August 2001, based on the idea that each and every embryo is a life too precious to sacrifice for any cause.

But that policy, which forbids federal funding of research involving any embryonic-stem-cell line created after President Bush's announcement, leaves some 400,000 embryos from in-vitro fertilization services (11,000 of which have already been donated for research) in frozen-storage limbo at U.S. fertility clinics.