It was a startling assertion that seemed an about-face from church doctrine: A Catholic hospital arguing in a Colorado court that twin fetuses that died in its care were not, under state law, human beings. When the two-year-old court filing surfaced last month, it triggered an avalanche of criticism—because the legal argument seemed to plainly clash with the church's centuries-old stance that life begins at conception. But it is also now fueling an already raging debate in Colorado and beyond about whether fetuses should have legal rights and, if so, what kind.