(RNS) It's a question that has perplexed philosophers, theologians and scientists for thousands of years.
Pythagorean Greeks, early Christian church fathers, Talmudic rabbis, Sunni and Shia scholars, Hindu Brahmin and modern bioethicists have grappled with the fundamental, ultimately unknowable, mystery: At what point in our biological development are we infused with a soul?
At what point do we become human?
Missouri lawmakers have declared their answer. By withholding both his signature and his veto, Democratic Gov. Jay Nixon signaled that he agreed and recently allowed the legislative answer to become state law.
''The life of each human being begins at conception," according to Senate Bill 793, which adds new regulations to the state's 24-hour informed consent law for abortions. "Abortion will terminate the life of a separate, unique, living human being."
The bill makes Missouri the second state to adopt such language after a similar provision became law in South Dakota in 2005, and then survived a legal challenge in federal court in 2008.
Abortion providers will be required to include the language from the bill "prominently" on brochures that will be required for every woman seeking the procedure — even if they don't happen to believe the Christian theology the words represent.
''Those are not sentiments that all the world's religions, or all the people in the state, believe in," said Paula Gianino, president and CEO of Planned Parenthood of the St. Louis Region and Southwest Missouri.
But supporters of the new law say they see no conflict between religion and the law's definition of life.
State Sen. Jim Lembke, a Republican and one of the bill's sponsors, said the language on the new brochures "is not a religious statement. It's a scientific statement."
Those with differing beliefs "will have to take all the information given to them and make an informed decision," Lembke said.
The sentiment expressed in the first of the new brochures' two sentences — that life begins at conception — has been part of Missouri law for nearly a quarter century. Scientists agree that when a sperm and egg unite, a living organism results.
But for philosophers and theologians, things get more complicated with the second sentence about abortion ending the life of a 'separate, unique, living human being."
''The distinction is between human life where you're talking about an organism as opposed to a human life in a moral sense," said Bonnie Steinbock, professor of philosophy at the State University of New York at Albany. "Those are two different debates that go back to Aquinas and the issue of ensoulment."
Aquinas, and Augustine before him, wrestled with concepts first introduced by Aristotle in the fourth century B.C. Aristotle believed that a soul could only inhabit a fetus when that fetus began to look human, a timetable he set at 40 days for men and 90 days for women.