Philosophical Ramblings #09: What is the self?

July 11, 2025

One interesting question is: What is the self? By that, we mean identity: what defines who you are. This question has interesting consequences depending on which model of identity you adopt. So, what models exist?

1. Identity as the Body

This is the first basic definition we might come up with: in this model, what makes you you is your body. In other words, person \(P_1\) at time \(t_1\) is identical to person \(P_2\) at time \(t_2\) if the body of \(P_1\) at \(t_1\) is the same as the body of \(P_2\) at \(t_2\).

• A superficial problem with this definition is that our bodies change constantly: cells die and are replaced, our hair turns gray, we go bald, we get wrinkles, etc.
• Perhaps we could define the body in a way that excludes such minor changes.
• A more serious issue arises with brain transplants. Suppose we switched the brains of two people. We would not say that your current body with someone else’s brain is still you. Instead, we would say that you are wherever your brain has been transplanted.
• Thus, this definition fails.

2. Identity as the Brain

Building on the previous point, we might say that identity is defined by the brain. That is, \(P_1\) at \(t_1\) is identical to \(P_2\) at \(t_2\) if the brain of \(P_1\) at \(t_1\) is the same as the brain of \(P_2\) at \(t_2\).

• Again, we face the superficial problem that our brains change over time: cells die, connections change, but let’s set that aside.
• The deeper problem is this: what if we copy your brain molecule for molecule, atom for atom? We build an exact replica of your brain and then copy all your brain signals into it. Functionally and physically, it is now identical to your original brain. But which one is you? Are you in the original brain or the copied one?
• Most people would say that the copied brain is not you, and that you still reside in the original. So, this definition also has serious flaws.

3. Identity as Psychological Continuity

What if we define identity not in terms of physical characteristics, but in terms of psychological continuity, i.e. a continuity in thoughts, beliefs, and mental states over time? In this case, \(P_1\) at \(t_1\) is identical to \(P_2\) at \(t_2\) if there is a continuous chain of psychological states from \(P_1\) to \(P_2\).

• As before, we encounter the problem that our psychological traits change drastically over a lifetime. Our desires, beliefs, morals, and even memories evolve or disappear.
• But again, perhaps we can assume that some core continuity remains.
• The deeper problem can be illustrated with teleportation: imagine a future where we’ve developed teleportation technology. Your body is scanned, atom by atom, destroyed, and reassembled elsewhere in identical form. Psychologically, the copy feels and thinks exactly like the original. According to this model, there is psychological continuity, so identity should persist. But intuitively, many feel the original has died, and the copy is just that: a copy.
• See Parfit’s Teleportation Paradox for more on this.
• Another example is someone with advanced dementia. Despite a total loss of psychological continuity, we often still regard them as the same person. This raises doubts about continuity as the defining factor of identity.

4. Identity as Consciousness

Another model of identity is based on consciousness: what makes you you is the unique way it feels to be you. That is, \(P_1\) at \(t_1\) is identical to \(P_2\) at \(t_2\) if the conscious experience (what it’s like to be) at both times is the same.

I tend to favor this fourth definition. Why?

One empirical reason comes from cases of split-brain patients. In rare, extreme cases (e.g., due to epilepsy), the connection between the brain’s hemispheres is severed. The result seems to be two separate centers of consciousness within one body. Consciousness, in other words, appears divisible. Similarly, if we connected two brains with a high-bandwidth interface, it’s plausible we could merge two consciousnesses into one.

In either case, splitting or merging, I would argue that a new consciousness emerges, with a fundamentally different experience of being. That means it is not you. (See Sam Harris’s account in Waking Up for more.)

However, there’s a problem with this model too: conscious experience is constantly shifting. How it feels to be you now is different from how it feels after a meal, or when waking up, or when falling asleep.

So what this model suggests is that there is no stable, continuous self. The “self” is always changing. Every shift in experience gives rise to a new self. There is no enduring identity.

Moral Implications

This fourth definition has fascinating moral implications.

If there is no continuous self, then the affection or concern we feel for our future self should be no stronger than the concern we feel for others. It’s plausible that the conscious experience of a 20-year-old man is closer to that of another 20-year-old than to his future 80-year-old self.

In this sense, you are more closely “your classmates” than “your older self.”

This undermines egoistic claims that we should prioritize our own future over others. If there is no continuous self, then stealing or hoarding money for your future self is no more justified than doing so for someone else. You should, by this logic, be equally willing to steal or save for your peers as for “yourself,” because your future self isn’t really you in any meaningful sense.

If the self doesn’t exist as a continuous, unified entity, then it cannot be treated with privilege.