Being pro-life used to mean, at a minimum, that you believe life begins at conception and that this life is worthy of protection at all stages of development. Sen. Bill Frist would like to "modify" that just a bit.

First, a little background. On August 9, 2001, you'll recall, President Bush announced a compromise. He would allow federal funding of embryonic stem-cell (ESC) research. But he restricted this government support to the 78 or so ESC lines that had already been created as of that date, "where the life and death decision has already been made." Thus, Bush said that the government should not encourage, nor should taxpayers pay for, research that involves the destruction of human life. At that time, Frist, who is a heart- and lung-transplant physician, announced he would support the policy.

Scientists value stem cells because of their purported ability to grow into other kinds of tissue and inaugurate a new era of regenerative medicine. "In all forms of stem-cell research," Dr. Frist said Friday, "I see today … great promise to heal. Whether it's diabetes, Parkinson's disease, Lou Gehrig's disease, or spinal cord injuries, stem cells offer hope for treatment that other lines of research cannot offer."

Currently, there are two kinds of stem cells. The first is so-called adult stem cells, derived from umbilical cord blood and other areas of the human body. So far adult stem cells have provided treatments for at least 65 conditions in humans.

The second kind comes from human embryos. Scientists value these ESCs because they are pluripotent, having the ability to become any kind of human tissue. ESCs also have the ability to reproduce themselves indefinitely. So far, however, after 24 years of research using both mouse ...