This question oversimplifies life, as if life were binary. It's not like turning on a light. Just because one subgroup of people has a strongly dualistic view of life does not give that group the right to legislate on the basis of that narrow view. Whose life is it? When do those cells stop being an extension of the life of the woman in whose uterus the embryo grows? None of us has the ability to determine when "life" starts, much less legislate it.