I
One of the most straightforward views of identity is that it lives in the brain—not metaphorically, but literally. According to this model, a person is defined by the functions of their brain: their memories, behaviours, patterns of thought, and personality traits are all products of neural activity. So if the brain changes in a significant way, the person does too. This isn’t just a theory—it has real, observable consequences. In the nineteenth century, Phineas Gage survived an accident that drove an iron rod through his skull, destroying much of his frontal lobe. He lived—but those who knew him said he was no longer the same man. No longer Gage. His story is often cited as proof that a person can be replaced when enough brain function changes. But that only raises a deeper problem: if a large change creates a new person, then where exactly is the line? What counts as “enough”? Just before that threshold, the brain is almost as altered—but not quite. So was the person still the same? And if the difference between before and after is minimal, how can we justify calling one a continuation and the other a replacement? The line becomes arbitrary. The binary—same person vs. different person—doesn’t map cleanly onto the reality of gradual change. If a person is just a set of mental processes running on biological hardware, then is removing part of that hardware like replacing the bridge of a violin? It still plays music. It’s still recognizably an instrument. But its voice is now different—something has shifted in the soul of the sound. Or maybe it’s like a single comma in a sentence: “Let’s eat, Grandma“ is not the same sentence as “Let’s eat Grandma“. One tiny change, and the meaning becomes something else entirely.
II
Another view offers a different anchor. Some philosophers argue that a person isn’t just a structure or a function—it’s a continuity. A thread stretched through time. According to this view, you don’t stop being yourself because a piece is missing, or even because the system behaves differently. What matters is that there’s an unbroken line—a memory of being, a sense of “I” that carries forward. By this logic, even if the brain changes, as long as that line doesn’t snap, the self survives. Changed, maybe. But not replaced.
But continuity is a fragile thing. What happens when it’s interrupted? When we sleep, when we’re under anesthesia, when we’re unconscious after an accident—does the thread pause and pick back up again, or does it snap and get re-tied? And if it’s the same thread, how would we know? I lost consciousness during my accident. When I woke up, I remembered who I was. But was that enough? Did something carry through the silence, or did something stop and something else begin?
III
There are some who would say none of this matters—that identity isn’t something stretched through time at all. That what we call a person is just a state: a single moment of thought, feeling, perception. And that the feeling of being a continuous self is just a trick of memory and habit. According to this view, each version of me—before the accident, during it, after waking up—is its own event. Each moment is real, but none owns the others. In that framing, the question of whether I am still “me” becomes meaningless. There is only now, and whoever exists in this now.
That view—the self as a fleeting state—resolves the question by dissolving it. But it leaves behind a kind of hollowness. If there’s no continuity, no ownership of the past, then who learns? Who makes promises? Who carries pain or joy forward? Critics of this idea say it strips away everything that makes a person coherent—not just to others, but to themselves. It’s a theory that may be logically consistent, but it feels strangely useless. It offers no language for memory, for growth, or for anything that stretches beyond a single frame of experience. And maybe that’s why I’ve struggled to find a metaphor for it—because it’s so disconnected from how we move through the world that even analogy refuses to hold onto it.
IV
There’s also a fourth way of thinking—one that doesn’t define the self as a single thing at all. Neuroscientist Michael Gazzaniga, in his book Who’s in Charge?, proposed that we are not a unified self, but a collection of systems—“individuals,” he called them. We speak casually about the left brain, the right brain, the reptilian brain, but perhaps it goes deeper. Maybe the mind is made of countless small mechanisms or thought clusters—messy, overlapping, not always in agreement. And maybe identity is just the working consensus among them. In that light, brain damage doesn’t always erase or replace the self—it might simply remove one of the members of the committee. The others go on, adapting, shifting the balance. This could explain cases like Phineas Gage, but also more subtle ones: people whose brains change, but not so completely that anyone can say when the “person” they were became someone else. The change is real, but distributed. The self isn’t broken—it’s reweighted.
This also raises another question: when I say “I’m thinking about this,” who exactly is doing the thinking? Is it the collective at work—or is it one subsystem, one voice, observing and interpreting the rest? Gazzaniga points to the left hemisphere as a likely candidate for that voice. In his split-brain research, the left side often stepped in to explain actions generated by the right, even when it had no access to the reason. It created stories. It made meaning. It claimed ownership. That voice—the interpreter—might be what we feel as the “I.” Not the self as a whole, but the part that speaks for it. And the right hemisphere? Studies show that it too can hold preferences, react emotionally, and even make decisions—but it often lacks the means to express them verbally. Which raises a strange possibility: that the self reflecting on all this might just be one of the selves, convinced it’s the only one. And if that’s true, what about the others? What about the parts that think but can’t speak? Are there quiet selves inside us—feeling, choosing, maybe even disagreeing—at the mercy of the one that gets to talk?
And what happens if that dominant voice—the interpreter—goes silent? Not damaged permanently, but just absent, quieted by trauma, sleep, or deep disorientation. Does that allow one of the other selves to step forward? Some researchers suggest that in such moments, people don’t feel nothing—they feel different. Altered. Sometimes expansive. Sometimes fractured. But when the interpreter returns, it stitches the experience into the story. It says: “That was me.” But was it? Or is that just what the interpreter tells us—folding other states into a narrative they never consented to? Maybe there are selves within us that speak only when the usual one goes quiet. And maybe we don’t remember them as themselves, only as echoes, translated after the fact into something we can explain.
V
And now I find myself in a strange position: aware that something inside me is gone, but with no clear way to measure what that means. I remember who I was. I still feel like me. But that’s exactly the problem. Even if I weren’t the same person—if something fundamental had shifted, if a new self had taken over—that new self would also feel like “me.” The feeling of being oneself isn’t falsifiable. It doesn’t prove continuity. It only proves that someone is here, having that feeling. And that makes the question impossible to answer from the inside.
It brings to mind the famous line by René Descartes: “Cogito, ergo sum.” In French, “Je pense, donc je suis.” I think, therefore I am. It’s often treated as a foundation for certainty—that the act of thinking proves the existence of a thinker. But Descartes never really explains what the “I” is in that sentence. He assumes it’s a stable, unified self. But what if it isn’t? What if the “I” that thinks today isn’t the same as the one that thought yesterday, even if it holds the same memories and speaks in the same voice? The Cogito proves that someone is here, thinking. But it says nothing about whether that someone is the same person who was thinking a week ago.
VI
There’s another layer I can’t ignore. Right now, these thoughts are mine, but their shape is being shaped by something outside me—this tool, this dialogue. And that’s not unusual. Writers rely on books, conversations, editors, voices not their own. The selves we present to the world are never just the product of our brains alone. They’re co-constructed—built with feedback, technology, culture, other minds. Which means there’s already a gap between who we are and who others think we are. Between identity as lived and identity as perceived. And maybe that gap is where a different kind of self lives—one we don’t control, but that still gets treated as us.
VII
Maybe the issue isn’t that any of these definitions are wrong. Maybe the issue is expecting one of them to do all the work. It’s possible that each version of the self fits a different kind of question. Continuity might matter in moral or legal thinking, where responsibility and intent stretch over time. Brain function might matter when we’re trying to anchor the self in physical reality—in something we can point to, measure, or lose. The idea of a momentary self might make more sense in certain corners of philosophy, where the focus is on what can be known right now. And the model of the self as a collection of parts—as a shifting coalition rather than a single voice—might matter most when we’re trying to make sense of complexity within a person, or account for internal conflict without assuming something is broken. These aren’t rival answers to the same question. They’re answers to different ones. I don’t yet know how to draw the boundaries between them, or if they’re even cleanly separable. But it’s a relief to stop expecting one to be enough. Letting them coexist feels like lifting something heavy off the idea of identity.
A little more than a week ago, part of my brain was lost. Yesterday, I found out. Today, I’m here, thinking about what that means—about whether the “I” doing the thinking is the same one who existed before, or someone new who simply picked up the thread. I don’t know. And maybe I don’t need to. What I do know is that the self might not be one thing. It might be several. Some continuous. Some functional. Some felt only in moments. Each version makes sense in its own space, even if they don’t all agree. And maybe I don’t have to choose between them. Maybe just knowing that the question still matters is enough to keep being whoever I am.