The so-called heartbeat bill has shifted from the South to Midwest, swerving eastward to threaten Pennsylvania. This week, two Pennsylvania Republican lawmakers proposed legislation that would ban abortion after a fetal heartbeat is detected, which usually occurs around six to eight weeks gestation. Gov. Tom Wolf has vowed to veto any antiabortion legislation.

More than a dozen states have introduced heartbeat bills, with several states adopting the policy. Just three weeks ago, a federal judge temporarily blocked a heartbeat bill enacted in Georgia.

As a university professor, I teach courses in biomedical ethics and philosophy of personhood. Human embryos, and their relation to ethical issues in stem-cell research and abortion, are a common discussion topic in my classes. One issue raised by the bill is whether a heartbeat is detectable at the sixth week of pregnancy. Medical experts suggest it is not. The mere detection of electrical activity coupled with a pulse hardly amounts to an identifiable heartbeat.

But, for the sake of argument, suppose a heartbeat were detectable. What exactly is that supposed to settle? Not viability; not the rights of women; and most certainly not whether the embryo is a person. Dogs and kangaroos have heartbeats, but that hardly makes them people.

As a thought experiment in my classes, I often propose this scenario first written by George Annas: Suppose you are in a fertility clinic when a fire breaks out. In one corner of the room is a 5-year-old girl lying on the floor, knocked unconscious from a fiery blast. In another corner lies a tray of 20 frozen human embryos. The fire is raging and you only have time to save one. Which do you choose? The girl or the embryos?

I have addressed this question to hundreds of students over the years. Not a single person has ever chosen the embryos. Everyone saves the girl.

The idea behind the hypothetical is that moral status of human embryos pales in comparison to the moral status of the girl. The girl, undeniably a person, deserves the moral respect that dignity demands. Conversely, embryos, despite belonging to our biological species, do not demand the same level of respect as persons.

Many antiabortion advocates have steadfastly argued that personhood begins at conception. The argument for heartbeat bills alongside the thought experiment places them in a paradoxical position.

On the one hand, if personhood starts at conception, why emphasize heartbeats? If you believe that, six weeks would be too late. The only answer here could be one of political expediency, not principle. On the other hand, if persons really start at conception, why does everyone choose to save the girl? Saving 20 persons over one girl would seem to be the only ethical option, even if tragic.

I am willing to bet that even most pro-lifers would forego the embryos and save the girl. (After all, if you escaped the burning building with the embryos, could you face the dead girl’s parents?) If saving the girl aligns with everyone’s ethical intuitions, that’s a good reason to believe that embryos are not persons. Heartbeat or not, a six-week ban on abortion is scientifically and ethically irresponsible and represents yet another assault on women’s bodies and lives.

Patrick Denehy teaches philosophy at Rutgers University-Camden and Drexel University, and persuasive business writing in the Wharton School at the University of Pennsylvania.