photograph of elongated shadow of person on paved road

Evie Toombes just won a lawsuit against her mother’s doctor. She was born with spina bifida, a birth defect affecting her spine, which requires continual medical care. Taking folic acid before and during pregnancy can help reduce the risk of spina bifida, but Toombes says that the doctor told her mother that folic acid supplements weren’t necessary. The judge ruled that, had the doctor advised Toombes’ mother “about the relationship between folic acid supplementation and the prevention of spina bifida/neural tube defects,” she would have “delayed attempts to conceive” until she was sure her folic acid levels were adequate, and that “in the circumstances, there would have been a later conception, which would have resulted in a normal healthy child.” The judge therefore ruled that the doctor was liable for damages because of Toombes’ condition.

Let’s assume that Toombes is right about the facts. If so, the case may seem straightforward. But it actually raises an incredibly difficult philosophical conundrum noted by the philosopher Derek Parfit. Initially, it seems Toombes was harmed by the doctor’s failure to advise her mother about folic acid. But the suggestion is that, if he’d done so, her mother would have “delayed attempts to conceive,” resulting in the “later conception” of a “normal healthy child.” And, presumably, that child would not have been Evie Toombes. Had her mother waited, a different sperm would have fertilized a different egg, producing a different child. So had the doctor advised her mother to take folic acid and delay pregnancy, it’s not as though Toombes would have been born, just without spina bifida. A different child without spina bifida would have been born, and Toombes would not have existed at all.

It may be that some lives are so bad that non-existence would be better. And if your life is worse than non-existence, then it’s easy to see why you’d have a complaint against someone who’s responsible for your life. But Toombes’ life doesn’t seem to be like this: she is a successful equestrian. And anyway, she didn’t make that claim as part of her argument, and the court didn’t rely on it. However, if Toombes’ life is worth living, and if the doctor’s actions are responsible for her existing at all, it might seem puzzling how the doctor’s actions could have wronged her.

The non-identity problem arises in cases like this, where we can affect how well-off future people are, but only by also changing which future people come to exist. It’s a problem because causing future people to be less well-off seems wrong, but it’s also hard to see who is wronged in these cases, provided the people who come to exist have lives worth living. E.g., it seems that the doctor should have told Toombes’ mother about folic acid, but, assuming her life is worth living, it’s also hard to see how Toombes is wronged by his not doing so, since that’s why she exists.

The non-identity problem also has implications for many other real-world questions. For instance, if we enact sustainable environmental policies, perhaps future generations will be better-off. But these generations will also consist of different people: the butterfly effect of different policies means that different people will get married, will conceive at different times, etc. Provided the (different) people in the resource-depleted future have lives worth living, it may be hard to see why living unsustainably would be wrong.

(It might be plausible that the doctor wronged Toombes’ mother, whose existence doesn’t depend on his actions. But wrongs against currently-existing people may not be able to explain the wrong of the unsustainable environmental policy, provided the bad effects won’t show up for a long time. Some unsustainable policies might only help current people, by allowing them to live more comfortably. And anyway, the court thought Toombes was also wronged: she’s getting the damages.)

Because it is relevant to important questions like this, it would be very handy to know what the solution to the non-identity problem is. Unfortunately, all solutions have drawbacks.

An obvious possibility is to say that we should make the world as good as possible. Since well-being is good, then, all else equal, we would be obligated to make sure that better-off people exist in the future rather than worse-off ones. But the decision of the court was that the doctor wronged Toombes herself, not just that he failed to make the world as good as possible: if that was the problem, he should have been ordered to pay money to some charity that makes the world as good as possible, rather than paying money to Toombes. And anyway, it isn’t obvious that we’re obligated to make sure future generations contain as much well-being as possible. One way to do that is by having happy children. But most people don’t think we’re obligated to have children, even if, in some case, that would add the most happiness to the world on balance.

Another possibility is to say that we can wrong people without harming them. Perhaps telling comforting lies is like this: here, lying prevents a harm, but can still be wrong if the person has a right to know the painful truth. Perhaps individuals have a right against being caused to exist under certain sorts of difficult conditions. But notice that we can usually waive rights like this. If I have a right to the painful truth, I can waive this right and ask you not to tell me. People who haven’t been born yet can’t waive rights (or do anything else). But when people are not in a position to waive a right, we can permissibly act based on whether we think they would or should waive the right, or something like that. You have a right to refuse having your legs amputated. But if paramedics find you unconscious and must amputate your legs to save your life, they’ll probably do it, since they figure you would consent, if you could.  Why not think that, similarly, future people whose lives are worth living generally would or should consent to the only course of action that can bring them into being, even if their lives are difficult in some ways?

A third solution says that Toombes’ doctor didn’t act wrongly after all–and neither would we act wrongly by being environmentally unsustainable, etc. But that’s very hard to believe. It’s even harder to believe in other cases. Here’s a case inspired by the philosopher Gregory Kavka. Suppose I and my spouse sign a contract to sell our (not yet conceived) first child into slavery. Because of the deal, we conceive a child under slightly different circumstances than we otherwise would have, resulting in a different child. (Maybe the slaver gives us a special hotel room.) There’s no way to break the contract and keep our child from slavery. Suppose the child’s life is, though difficult, (barely) worth living. This solution appears to suggest that signing the slave contract is permissible: after all, the child has a life worth living, and wouldn’t exist otherwise. But that doesn’t seem right!

I wrote more about this in chapter eight of this book. There are other possible moves, but they have problems, too. So the non-identity problem is a real head-scratcher. Maybe someone reading this can make some progress on it.

Dustin is currently a postdoctoral researcher at the Ludwig Maximilian University of Munich. He received a PhD from the University of Notre Dame in 2018, and specializes in social and political philosophy, ethics, and the intersection of these two fields and philosophy of religion.