About 270 years ago, the Scottish philosopher David Hume, in his seminal work “A Treatise of Human Nature,” offered what was, at that time, a radical notion of human identity: that the “self,” as we conceive of it, is not a single spiritual or psychological entity, like a “soul,” but rather a collection of discrete sensations and impressions — a “bundle,” as he called it. Connections between these individual perceptions give rise to the idea of a continuous “self.” And memory gives that self lasting force.
What, then, is a self without memory? Or, rather, what would happen if we were to remove some memories and add others? By Hume’s account, the bundle would change, and so necessarily would the self. We would be different people, in small but significant ways.
These days, this thought experiment lives mostly in the minds of college freshmen taking their first philosophy seminars. But increasingly, the idea that altering one’s memory could alter one’s self is gaining relevance outside the confines of the Ivory Tower, as new scientific advances offer the promise of re-engineering one’s brain chemistry — and, possibly, re-engineering one’s self.
The most recent example is an announcement by two scientists at Johns Hopkins University that they may have discovered a way to erase traumatic memories from the mind by removing certain proteins from the amygdala, the brain structure that processes memory and emotional reactions.
The procedure is still theoretical, and primitive, but Richard Huganir, a professor and chair of the neuroscience department at the Johns Hopkins School of Medicine, told the Baltimore Sun on Monday that the discovery “raises the possibility of manipulating those mechanisms with drugs to enhance behavioral therapy for such conditions as post-traumatic stress disorder.”
As the Sun article points out, the idea of manipulating a person’s brain chemistry to dilute the power of a painful memory is not entirely new. Some medications that target the amygdala are already used in behavioral therapy to lessen the emotional impact of traumatic memories in patients suffering from PTSD.
But the Hopkins discovery goes further, proposing to remove certain “receptor proteins” that facilitate the creation of painful memories. The scientists say they would be able to isolate the memories by having the patients recall those events, identifying the proteins responsible and administering therapy to remove those proteins, thus erasing the memory. Huganir also wrote in a paper for Science Express last week that a similar mechanism might be at work in other centers of learning in the brain, and that such memory-erasure therapy could eventually be used to treat drug addiction or physical pain.
In this context, Hume’s theory of personal identity proves a useful thought experiment: Most of us tend to think there is something essential, or irreducible, about our “selves” that cannot simply be altered or erased by a chemical in the brain. Upon reflection, the idea of erasing a memory seems inherently threatening to our personal identities. We think of our own memories, the events in our lives that have shaped our characters and inform our everyday decisions, and wonder how we would be different without them. And these are only the memories that we recall; the others, which lurk beneath the surface of the conscious mind — what’s known as “implicit memory” — are perhaps just as important.
Then again, it’s possible to see Huganir’s discovery as providing choice, liberating patients to choose what sort of person they want to be. Say, for example, a patient suffering from PTSD decides that she prefers not to be the person she is at that moment, but the person she was before the painful events in question took place. Who’s to say this isn’t a valid choice? And perhaps that choice is, in itself, what makes us who we are. Perhaps Hume’s idea of the self is wrong, as is the idea of an essential, inalterable self. Perhaps the self is simply what we choose, for ourselves, to be — even if that involves erasing the memories we no longer want.