The abortion issue is immensely complicated, and our position about it largely depends on how we answer several questions. One of those questions is, “when does life begin?” This sounds so simple to answer, but it couldn’t be more complicated. I’m a scientist, that’s what I do for a living. I have advanced training in these things, and I have no idea how to answer that question factually, and believe me I’ve tried. I’ve looked for evidence that I can use to help form my opinion about this part of the issue, and it’s one of the few areas where I honestly feel there is no scientific answer to the question. It’s simply not an empirical question.

Biologists have struggled with what it means to be “alive” for centuries. Generally speaking, “alive” is best defined by being different from its opposite, “dead.” Life is some quality of living things, that differentiates them from non-living things. It includes metabolic activity, capacity for things like growth, development, reproduction, and response to stimuli. From that perspective, the embryo, the fetus, the sperm, the egg, the cancer cell growing inside of us are all alive. But this isn’t really what people mean when they talk about the fetus being “alive.” In some ways, this is why the question “when does life begin” isn’t even the important question, although it’s phrased that way. “Do you believe that life begins at conception?” Well, no, because the sperm and egg were already alive, so I believe that life began a long time before conception.

I guess what’s important is that we’re not really asking when life begins (even though that’s the shorthand, and what people might think they’re asking), what we’re really asking is when do we have human rights. That’s a murkier question when it comes to humans of varying ages. Kids, for example, have lots of rights. We’re no more allowed to murder kids than we are allowed to murder adults, but we’re allowed to confine our children to their rooms without due process. We aren’t allowed to do that to adults. We don’t allow children to use recreational drugs, but adults can smoke and drink freely. Children do not have all of the rights that we protect for adults. Of course these are simple examples, and for the person who believes that the embryo has these rights, what I wrote above is of critical importance: we aren’t allowed to kill kids at any age. But that’s not entirely true, especially if we think about risks that we legally expose children to, risks that may lead to death, without their consent. We make medical decisions for our children, without their consent, some which carry a reasonable probability of death. We drive our children in cars, without their consent, and death by traffic-related injury is one of the most common causes of death for children 5-19 years old in the United States. No, I’m not arguing that driving a car and getting into a fatality accident is the same as killing a child, I’m just saying that the protection of human rights is simply different for adults than it is for children. This is a clear part of our society.

When it comes to the unborn, things get even murkier. For many people, the Bible is an important source on this issue. We can debate forever how much the Bible should or shouldn’t be a source upon which we base our laws, but given that I’ve already argued that this isn’t a scientific question, I think it’s fair to consider plenty of other sources. Unfortunately, the Bible isn’t all that clear. One passage that’s often used by people arguing that life begins before birth (really trying to argue that human rights begin before birth) is Psalm 139:13. David says to God, “For you created my inmost being; you knit me together in my mother’s womb.” This clearly shows that life begins “in my mother’s womb,” right? Well, it clearly shows that David says his life began in his mother’s womb, but is that the same thing? First of all, is David’s word as strong as the word of God? I’m not a Biblical guy, so I can’t answer that, but personally, I’d want to hear it straight from God. According to the Bible, Moses got to hear straight from God, and this is what God said (Numbers 5:11-31): If you think you’re wife is cheating on you, and there’s no witness, you should bring her to a priest, and the priest will mix holy water with dust from the floor of the tabernacle to create a bitter water that will cause a curse. If he’s right, and she’s pregnant (if thou hast gone aside to another instead of thy husband, and if thou be defiled…) the water shall “go into thy bowels, to make thy belly to swell, and thy thigh to rot…” It’s not difficult to read this as a prescription for a chemical abortion, carried out by the priest.

Then there are passages like Jeremiah 1:5 when God says, “I knew you before I formed you in your mother’s womb.” Others look to the language used in the Bible to refer to people before they were born. Genisis 25:22 reads “and the children struggled together within her” referring to Esau and Jacob while inside Rebekah. This, some argue, is perfect proof that the Bible says they’re “children” before being born, and have all the rights of children. But then there’s Numbers again…Numbers 3:15-16 and Leviticus 27:6 say that when counting people, only count males from one month old and upward. Exodus 21:22-23 makes it clear that if you hurt a woman and cause her to miscarry, as long as you don’t harm her (other than the miscarriage), you have to pay some money. If the woman dies too, then it’s an eye for an eye, a life for a life; but the unborn doesn’t evoke an eye for an eye, a life for a life.

So, even if non-religious people like me are willing to turn to the Bible for help here (not something I’m willing to do, but if I were), it simply doesn’t seem to be a reliable source here (“reliable” in the scientific sense — yielding the same result with each repeated trial; not “reliable” in the media kind of way: a reliable source is one that can be trusted). What other sources, then, can we use? Well, maybe our own behavior and our own feelings, emotions, and reactions to events, independent of how we think we feel? Personally, I think these things are often good measures of how we really think. Similar to my discussion about bias earlier, sometimes what matters more, and what’s a better indication of how we really feel, is how we react, not how we think we feel. We’re very good at fooling ourselves. In this respect, I think a critical thing to look at is how many people who otherwise consider themselves to be “pro-life,” meaning that they don’t think abortion should be legal, believe strongly that there should be an exception for some things. This is a sizable group. Gallup polling shows us that only 19% of Americans surveyed in May 2015 believe that abortion should be illegal in all circumstances. In contrast, 29% believe it should be legal in all circumstances, but, and here’s the number that matters here, 51%, a majority, not just a plurality, believe that it should be legal only under certain circumstances. This number has been as high as 58% in 2001 and has hovered at 57% for several years between then and now. Follow-up questioning in some years shows that more than 80% of those surveyed thought that abortion should be legal if the woman’s life is endangered, and more than 70% said it should be legal if the pregnancy was caused by rape or incest. My guess is that most people reading this won’t have a problem with this. Those who are in favor of abortion rights will happily agree that a woman who is pregnant as the result of rape or incest should be allowed to opt for an abortion, and the polling tells me that even many people who consider themselves “pro-life” (meaning anti-abortion) would be OK with this also.  It’s this group that’s the most informative to me.

Let’s look at somebody who considers themselves anti-abortion/pro-life, but who thinks it’s only fair that a woman who gets pregnant as a result of rape or incest should be allowed to terminate that pregnancy. This person likely opposes abortion because he/she feels that life begins at conception and that abortion is akin to murder. That seems to be the most common reason given for being against abortion. But doesn’t the acceptance of this exception, for conception by rape or incest, show that there is, in this person’s view, a difference between the fetus and a baby that has already been born? For the sake of this thought exercise, let’s accept the premise that a baby is a baby, with the rights of all babies/children/humans from the moment of conception. If that’s the case, why is it OK to kill the baby in the womb if it was conceived by rape or incest, but it’s not OK to kill the 2-year old child who was conceived by rape or incest? I don’t know anybody who believes that a mother has the right to kill an infant, toddler, teenager for any reason. Yet, this same person who thinks they believe that there is no difference between abortion and killing a baby, says that it’s OK to terminate a pregnancy if the pregnancy was the result of rape or incest, or if the mother’s life is at risk. This tells me that even though the person says that abortion is the same as killing a baby, they really don’t think that’s the case, or they wouldn’t agree that the woman has the right to abort (i.e., kill the baby) under any circumstance.

This leaves us with the original question: when does life begin? And my answer: we don’t know, we may never know, and it depends entirely on how you define “life.” We humans don’t like stuff like that. We like hard and set rules. We like to know that things are healthy or unhealthy, that things are good or bad, that others are our friends or our enemies. We like clean distinctions, but I think this is best summed up by the best president ever, the fictional President Bartlet:

Every once in a while, every once in a while, there’s a day with an absolute right and an absolute wrong, but those days almost always include body counts. Other than that, there aren’t very many un-nuanced moments in leading a country that’s way too big for ten words.