Often, contentious political and social questions have a scientific question in the middle of them. Resolving the scientific question will not always resolve the political ones, but at least it can properly inform the debate. The recent overturning of Roe v Wade has supercharged the debate about when human life begins. It may seem, then, that what  science has to say about this question is important to the debate. But it may be less useful than it at first appears.

For example, in a recent editorial Henry Olsen, who is pro-life, asserts – “The heart of the abortion debate: What is human life?” I actually disagree with this framing. That is often a subtle and effective way to manipulate a debate – you assume a certain framing of the question that is biased toward one side. In this case, if the question is – what is a human life – then the pro-life side only has to argue that a fetus is a human life. But this framing is wrong on multiple levels.

Olsen is trying to frame this as a scientific question, but really the abortion debate is much more of a philosophical question. First let’s address what science questions there are.

Is a fertilized human embryo “human life?” Sure. It’s a living organism, and it is certainly human. But that’s not the only question. One could also ask – when does a fertilized egg become a person? That is a more nuanced question. I think there is broad agreement that a baby is a person. At the other end of the process we have a single cell. That cell may have the potential to develop into a person, but the cell itself is not a person.

At what point does a clump of cells become an actual person (again – not just the future potential of one)? This is an unanswerable question, as there is no sharp dividing line. There is no definable moment. There are milestones we can use to make some reasonable judgement calls. For example, one might argue that a person has to have the capacity for self-awareness, some sense of self and of being. This requires at least a minimally functioning brain.

This is as good as science itself can get us. We can describe the biological functions of a fertilized egg, and the abilities of a fetus as it develops slowly into a person. But science cannot tell us what relative value to put on a fetus at varying stages of this development, how the potential for future development relates to that value, and what rights should accrue to a fetus at different stages of development.

Most importantly, science cannot tell us how to balance the relative rights of a fetus vs the woman who carries that fetus. Again, we can use science to inform thinking about how to balance these rights – is the fetus biologically dependent upon the mother for life, for example. This is the viability standard. Science can tell us when that happens, but not what the viability standard means ethically and legally. We can also use science to inform the discussion about the medical effects of pregnancy and birth on women, but not about how to weigh those effects toward the overall question.

So really the abortion debate is not a scientific one, because the role of scientific information, while important, is not determinative in any real way.  Those who want to reduce the debate down to a simple scientific question (what is human life?) are actually trying to just declare victory on all the thorny philosophical questions without explicitly stating so.

The real debate comes down to ethical philosophy and legal theory. How do we balance these various facts:

A human embryo is a human, but not sentient.

Sentience and personhood develops gradually throughout the pregnancy.

Fetuses are dependent on the life of their mother until they develop sufficiently to be viable outside the womb.

Pregnancy is a serious biological process with significant implications for the life of the mother.

Despite rather disingenuous (in my opinion) attempts at reframing the abortion debate, it has always been about how to balance the relative rights of the fetus at different stages of development with the rights of the mother over their own autonomy and their own bodies. This is a thorny ethical question without an objective solution.

There is also no analogous situation – nothing sufficiently similar that we can say that you have to have a certain opinion about abortion in order to be consistent with some other position – such as: if you think people in a coma have rights, then fetuses have rights, or if you think that people have certain rights to privacy and autonomy then that must include the right to abortion. There is no single slam-dunk philosophical argument for either side.

This often happens when there are competing ethical rights or principles – the two have to be balanced in often a nuanced and complex way. With abortion we have the relative rights of the unborn vs the rights of the mother. Most people tend to come down somewhere in the middle, with a position that the rights of the mother hold sway at first, but at some fuzzy point in the pregnancy the balance tips over to favor the rights of the fetus.

Again, there is no sharp unequivocal line to draw, but we can draw meaningful lines. We can use factors like probable viability, risks to the life of the mother, or whether or not the pregnancy was the result of rape or incest, in order to move the line back and forth to come up with the optimal balance of rights. Further, people can meaningfully disagree about exactly how to draw these lines. Therefore other ethical principles come into play, such as the balance between liberty and the concerns of the state, and where we should default when the debate has no clear resolution – who has the burden of proving their compelling interest is greater?

Generally in the US we tend to default to individual liberty, and the state has to demonstrate their compelling interest to interfere with that liberty. That would mean we default to a woman’s right to determine what happens with her own body. Further, we have to distinguish between personal moral choices (which may be informed by culture, religion, and personal attributes) vs objective ethical and legal philosophy, which is valid to impose on a society as a matter of law. We can agree as a society that stealing is unethical, make it illegal, and impose penalties for doing so. But we should be very cautious before making a moral decision, like marital infidelity, a criminal offense. That falls more in the realm of a personal moral choice, not something that should be policed by society.

Therefore we have to simultaneously consider not only when throughout a pregnancy the rights of the mother vs the rights of the fetus hold sway, but whether or not the judgement is objective enough to make it a law or whether or not it should be left to personal choice. Most people tend to come down in the appropriately muddled middle – during the first part of a pregnancy the mother’s rights hold sway and we should default to personal choice and liberty; during the end of the pregnancy, when the fetus is more of a baby and is potentially viable outside the womb, then the state can exert a compelling interest to protect the life of the baby. In the middle is the gray zone, but we have to draw lines somewhere. In addition there are special considerations, such as rape or incest. Also, if the life of the mother is at risk, and the choice is essentially between the life of the mother vs the life of the baby, that is an extremely difficult personal decision and it seems difficult to successfully argue that the state should get involved in that decision.

This is a tricky debate that we need to have, but it should be properly framed. This is a legal argument about how best to codify complex ethical philosophy. Science can inform some of the details, but this is not a debate that can be won entirely by “following the science” or trying to boil down the complex issues to one scientific question.