It should go without saying that the ability to selectively erase memories would be a very useful one to have (see “Repairing Bad Memories”). It could be used as a treatment for many people. Someone suffering night after night from PTSD that’s resistant to drugs or cognitive therapy might be able to erase or blunt the memories of combat, trauma, or rape, averting the career problems such intrusive thoughts might cause. Selective erasure of memories might also be a relief to the young child who cannot forget the horror of watching a parent die in an automobile accident, or the bystander who watched flesh and body parts litter the street after a bombing or plane crash.

But before we get overly enthusiastic about the prospect of drugs and cognitive tricks that might erase unwanted memories or block their formation, a number of thorny ethical questions need to be acknowledged and examined.

While getting rid of horrible memories sounds great, the research needed to fine-tune this process may require subjects to risk the loss or alteration of other, wanted memories. How much risk should these research subjects be allowed to take? The answer must take into account the dangers not only to their health but also to their sense of personal identity and selfhood.

Let’s presume that we really can learn how to target particular memories and get rid of or weaken them. Are we really all that certain that their loss will be our gain?

Sure, at one end of the spectrum are the demons that won’t let us be, that lead to insomnia, night sweats, addiction to sleeping pills or booze, and perhaps even suicide. But the fact that too many people are tortured by what they cannot forget does not mean everything unpleasant in the realm of memory is bad. Not all our worldly experience is pleasurable, but all of it can still be hugely meaningful and constructive for us to remember.

The inability to forget that person who cheated on you has been the lament of country ballads and popular music forever. But don’t we learn from our mistakes, and isn’t adversity a crucial part of what makes us who we are? What makes you modest, humble, introspective, deliberative, empathetic, and prudent—in short, virtuous—may be driven by memories of experiences that are unpleasant, disturbing, riveting, and shameful. I don’t like remembering my failures and errors, but as I struggle to be a better person, I most certainly would not to have then vacuumed out of my neural net or yours.

Some of our collective bad memories—of holocausts, mass murders, pandemics, natural catastrophes, and wars—are precisely the ones we may long to obliterate. The advice that we, humanity, must “never forget” such events is just as valid as the desire to erase them from our consciousness.

The ability to modify memory might also affect future behavior. In the law, making sure that fallible memories do not become extinct ones may be crucial to determining guilt or innocence. Soldiers or spies who can be sent to kill with the knowledge that they need not worry about troubling feelings afterward may be people you would not want for a serviceman, spouse, neighbor, or friend. A person swept free of unpleasant memories is a person who may lack empathy and sympathy, traits fueled by remembering how we felt when we screwed up, when we were bullied, or when our best-laid plans went awry.

There are questions of public policy, too. Hollywood’s fictional Men in Black kept the world safe from aliens by adept use of memory-erasing “neuralyzers” without informed consent. Many governments, industries, and organizations in the real world, too, might see value in memory erasure that is far from voluntary.

Memory erasure can be a powerful and valuable tool. But it is one requiring a good deal of ethical reflection and oversight lest it become a source of bad memories rather than a balm for them.

Arthur Caplan is a professor and founding head of the Division of Bioethics at New York University’s Langone Medical Center.