In the near future, the Supreme Court will likely decide whether to overturn two landmark abortion cases: Roe v. Wade (1973) and Planned Parenthood v. Casey (1992). If it does so, it will have to face the issue of when people begin to exist.

In Roe, roughly, the Supreme Court held that during the first six months, a state may regulate abortion only in ways that are reasonably related to a woman’s health. It may not protect the fetus’ life. The court reasoned that precedent did not view fetuses as people. It did not address the issue of when life begins because this is above its pay grade (specifically, it is not in a good position to speculate on the issue).

Following Roe, Casey imposed the following rule: A state may not impose an undue burden on a woman who wants to have an abortion before the fetus is viable. A fetus is viable when it can survive outside of the woman. The court said that an undue burden is a law that has the purpose or effect of imposing a substantial obstacle on pre-viability abortions.

Despite these Supreme Court decisions, Alabama recently criminalized abortion except when there is a medical emergency. Six states have trigger laws that would make abortion illegal were Roe overturned. Nine states still have pre-Roe abortion-prohibitions on the books. These prohibitions would likely take effect were Roe overturned. Various states limit or ban abortions past various threshold. Among the thresholds are the following: conception (one state), 6 weeks (four states), 20 weeks (14 states), 24 weeks (six states), 25 weeks (one state), and viability (18 states). A number of states require a waiting period, ultrasound, or counseling in part to discourage abortion.

The problem with these laws is that an individual begins to exist when he has has a brain, specifically, a brain with the capacity for thought. Prior to when a fetus has a brain, abortion is more similar to contraception than infanticide.

To see this, consider other views on when people come into existence. Some people think people come into existence when an organism begins to exist. This likely occurs at conception. On this theory, a person is an organism (that is, an animal). Others, usually religious folk, think that people come into existence when their souls come into existence. On this theory, a person is a soul or, alternatively, a soul is part of a person.

Consider the metaphysical arguments for the idea that a person begins to exist when his brain begins to exist and that he is located in whole or part where his brain is located.

First, imagine a case of one body with two heads. Each head has different thoughts than the other. In fact, there is a case of conjoined twins, the Hensel twins, that looks like this, although for technical reasons this is probably not such a case. For example, if the Joker were to shoot them with .50-caliber Desert Eagle, he would and should be charged with two murders. This case shows that a person is brain not an organism (animal). This is because the body with two heads is only one organism. Biologically, it is one animal in the same way that a lion with an extra set of lungs is one animal.

Second, you can imagine a case when we transplant one person’s head onto another person’s body and vice versa. Consider, for example, if we transplanted Bernie Sanders’ head onto Sylvester Stallone’s body and Stallone’s head onto Sanders’ body. After transplantation, it intuitively seems that Stallone see the world from atop Sanders’ flabby body and Sanders would see the world from atop Stallone’s chiseled body. Again, though, the animals did not switch places, only the brains did. This is not merely a thought experiment. A head transplant has been successfully performed on a monkey.

Third, it intuitively seems that when a person’s brain (or, perhaps, just her cerebral cortex) is destroyed, she no longer exists because she can longer think. This is likely what happened in the Terri Schiavo case. Terri’s forebrain dissolved before her body stopped functioning. As a result, Terri no longer existed, although her body still functioned. If this is correct, then a person comes into existence when her brain comes into existence.

The notion that a person comes into existence at conception faces yet another problem. Consider a zygote that splits to form twins. Consider, for instance, Ashley and Mary-Kate Olsen. Because they are not the same person, neither one was the zygote that split to form them. This is because if B and C are different people, then A cannot be identical to both without producing a contradiction. If this is correct, then they (and we) were never a zygote.

Religious people often believe that a person is a soul. This allows people to exist in heaven centuries after their bodies and brains have dissolved away. One problem with this view is that it is unsupported by science. A second problem is that it is unclear when a soul begins to exist. Proponents of this idea usually view the soul as the seat of consciousness. On this theory, then, a person begins to exist when he can become conscious.

Were Roe overturned, a number of these states would criminalize abortion before people come into existence. They would thus treat something that is the moral equivalent of contraception as if it were murder (or some other felony). That is not what freedom-loving people do.

The Supreme Court can’t keep ducking the issue of when people begin to exist. The Constitution limits what the federal government and states can do to people or what they can allow others to do to them. See, for example, the Due Process and Equal Protection clauses. If so, the court will have to face the issue of when people begin to exist. Enter the brain.

Stephen Kershnar is a State University of New York at Fredonia philosophy professor. Send comments to editorial@observertoday.com