Memory and Personal Identity

A fun topic for introduction to philosophy classes is that of personal identity. What is it that makes you the same person that you were ten years ago? Why should I care more about future versions of “me” than I do about future versions of “you,” and so on?

In day-to-day life we assume that sameness of body gets us sameness of person, and we have standard pragmatic ways of deciding whether something is the same body or not. Just as we can decide that the car I’m driving today is the same car that I took to the mechanic yesterday (despite the fact that some parts were replaced), I can easily conclude that the bodies of me and my friends are the same objects that were around years ago (despite the many changes they have suffered).

But you don’t have to be a philosopher to think up scenarios where our standard pragmatic criteria of whether something is the “same thing” break down. If the mechanic had to replace the engine of my car, it’s still the same car. But what if the the drive train and the exhaust had to be replaced as well? And the chassis? And the frame? At what point do we say that it’s no longer the same car, but is instead a new car that didn’t previously exist?

This puzzle (known to philosophers as the problem of “Theseus’s Ship”) might not trouble us too much when it comes to inanimate objects like cars and ships, because we might suppose that it doesn’t need an objective non-arbitrary answer. Perhaps we can just decide whether we want to treat the car as the same car or a different car in these cases.

But this answer seems far less plausible when I ask whether I would survive some transformation or not. It seems obvious that I could survive, for example, losing a kidney and getting a replacement. It would still be me who would would wake up from transplant surgery after getting a new kidney, or heart, or leg — it wouldn’t be some new person. But just how far can this go?

Suppose, for example, that there was a device that would completely disassemble your body and then reassemble it later at another location (either from the old matter, or from new matter).


Would you survive such a process? Or would this be the death of you and the new beginning of someone else?

One of most popular answers among philosophers says that you would survive, just so long as the reassembled body had memories of your earlier life, had the character and desires, and so on. That is, it’s you just in case the being is “psychologically continuous” with you.

Now this doesn’t solve everything (after all, what if two beings are recreated after you are dissolved on the Star Trek transporter pad?), but it’s a pretty attractive view and one that has a large number of prominent defenders (past and present).

But if memory is essential for making us who we are, then what are the ethical implications of changing our memories (and perhaps our other psychological characteristics)? Not surprisingly, science fiction has already asked this question (though, also unsurprisingly, it hasn’t definitively answered it).


Recall that in the movie that takes place either on Mars or in Arnie’s head it turns out that the protagonist (Arnie) discovers that earlier in life, he (or someone else in his body) had been a really bad guy who was bent on exterminating the good mutant rebels on the red planet. This pre-Arnie person then had his memories removed (or “capped”) and had is brain rewired to be a nice guy.

The nice-guy Arnie then fights for the freedom of the good mutant rebels, and refuses to revert to “his” former evil self. In the end he activates some alien technology, kills the bad guys, gets the girl, saves the planet, and all the other things that Arnie is contractually obligated to do in his movies. (The web was mightily amused at Schwarzenegger’s DVD commentary on the movie a while back; enjoy it here.

The philosophical question is this: Is Arnie (or more accurately, his character — but c’mon, Arnie is Arnie) guilty of the crimes committed by pre-Arnie (i.e., by the evil guy who previously inhabited his body)? If you were on a jury and had all the facts of the movie laid out before you, would you put the now-nice guy in jail, even though he doesn’t even remember committing those crimes and even though he now would never act in such an evil way?

Fun for philosophy, but this also has real-world implications. People do lose their memories and they do undergo changes in personality (sometimes quite severe). What is the relevance of this for questions of moral responsibility, and for the question of whether a person is in fact the very same person as she was before the memory loss?

Alison Winter raises related questions in an article in Salon, drawn from her book Memory: Fragments of a Modern History. (Which is what prompted this post, though I really don’t have too much to say about it — I mostly wanted a link so I can find it for my students in the future.) The issue that Winter confronts is the ethics of erasing painful memories (for example, of soldiers suffering from post-traumatic-stress disorder). On the one hand, deleting such memories might make people happier. On the other hand, some would argue that there’s a huge price attached to such memory tampering: it might literally undermine the very foundation of what makes you who you are.

A related issue that I don’t see Winter discussing in the article (perhaps she does in the book), is that of memory blocking agents that are added to sedatives any time you’re knocked out for surgery. I don’t know all the details (but I have had some fun conversations with anesthesiologists at parties), but the basic idea is that the gas they give you before and during surgery has three main components. One to render you unconscious (which is what we all think of), one to paralyze you (so your body doesn’t involuntarily react and make things difficult for the surgeon), and one to prevent the formation of any memories while you’re under.

So, why is that last component there? The usual justification is that if you do feel any pain during surgery, you’ll be better off later if you don’t remember it. One wonders, however, to what extent fears of malpractice lawsuits are a motivating factor.

This example is sometimes raised by philosophers arguing against behaviorist accounts of conscious experience (you wouldn’t be willing to undergo surgery while paralyzed and having your memory blocked if you were still conscious, even though behaviorally the chemical that renders you unconscious doesn’t make a difference), but we’re more interested in the memory question at the moment.

If something very unpleasant is going to happen to you, would you want to have any memories of it? Would you want to have your painful memories erased? How many memories would you be willing to give up? How many memories could you lose and still be “you”?

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