To a physicalist, the only way to interpret the question "why am I me and not someone else?" is "why is my physical body identical to my physical body and not identical to another physical body?". The framework simply doesn't allow alternative interpretations. This interpretation is a tautology, because in the universe, things are identical to themselves, and only to themselves.
If you are using an abstract definition of "yourself" (such as your brain's internal representation of you), you are no longer talking about physical objects, so of course your question can't be answered using physical facts alone. Similarly, "2+2=4" is a statement about our abstract representation of the world, not the real world itself. That we can reason about integers without relying on facts about the real world doesn't mean that integers are any more "real" than unicorns - or for that matter, your concept of "self".
That's why it's a good argument against physicalism. According to what you just said, everything we ever experience is talking about "not the real world itself" according to physicalism, therefore why does it ever make sense to assert the "real world itself" over what we actually experience? It's like watching a movie and believing in the movie more than the fact you are sitting watching a screen.
> According to what you just said, everything we ever experience is talking about "not the real world itself"
I don't know how that follows from what I said. When someone says "the floor is slippery", that refers to a very much real physical property of a very much real thing. When someone says "the floor is lava", that means we're playing a game. We have no problem distinguishing between the two.
If you define yourself as the set of atoms that currently make you up, you are talking about the real world. If you define yourself as the set of your memories and experiences, you are not. The former definition has a lot less issues than the latter - firstly because you don't have to define anything further, you can just point at yourself; and secondly because a perfect clone of you would have the same set of memories and experiences, and that doesn't make them you. This is why "Why am I myself?" is much easier to answer when we're talking about your atoms. Now, if a theory can answer a question with ease, how is that question an argument against it? I've certainly never heard anyone say "If global warming is real, why are my car tires melting into the asphalt?".
> Now, if a theory can answer a question with ease, how is that question an argument against it?
Bowsamic may have a different take on this, but in my version of the argument, the point is not to answer the 'why' question. The 'why' question is just used to gesture at the relevant non-tautologous and apparently non-physical fact. So it doesn't really help with anything to redefine the terms of the question until it becomes a tautologous statement about atoms. All that shows is that physicalism doesn't have a problem with the concept of two physical things being the same thing – which isn't in dispute.
>If you define yourself as the set of atoms that currently make you up [...]
I don't see how I'm going to do this without some prior notion of who I am. Otherwise, one set of atoms is as good as any other.
> The 'why' question is just used to gesture at the relevant non-tautologous and apparently non-physical fact
Yeah, but to clearly define what that fact means, you'd have to introduce a bunch of intermediate definitions, and eventually you might just end up in physics-land again. It isn't physics' fault that the human brain is complicated.
> I don't see how I'm going to do this without some prior notion of who I am
Protip: if you pinch it and it hurts, it's probably yours :) Well, that or a very angry cat.
To be more serious: having prior notions of things is fine. Required, even. We can't reason about things without having at least a vague understanding of the language. It can't be turtles all the way down.
>and eventually you might just end up in physics-land again.
Sure, anything might turn out to be explicable by future physics (or indeed, future astrology, future phrenology, or any possible future knowledge). There are no knock-down arguments in this domain. The point is that the fact of your personal conscious identity is apparently not a physical fact, which is a prima facie argument against some of the stronger forms of physicalism.
>To be more serious: having prior notions of things is fine.
You can't use the physical definition to dispense with other notions of personal identity if you need those very notions to bootstrap the physical definition (and maintain it over time, as your 'set of atoms' is constantly changing). To point out that your informal notion of self is connected somehow with a loosely-defined lump of physical stuff isn't really to succeed in reducing anything to physics. It's just to say what pretty much everyone agrees with: that humans have physical bodies.
> You can't use the physical definition to dispense with other notions of personal identity if you need those very notions to bootstrap the physical definition
Now that you mention, I don't need to. "I" simply means "the person who is currently speaking" (or in this case, writing). This already determines, beyond reasonable doubt, which physical body we're talking about. No other definition needed, since you can't say "I" without speaking. QED. Sorry, I should have noticed this 4 comments earlier.
(Caveat: this definition doesn’t feel satisfying, which might be the source of our disagreement, but I can’t put my finger on why - perhaps you can)
> the fact of your personal conscious identity is apparently not a physical fact
The human brain is astonishingly good at BS-ing itself, so I wouldn't attribute much to how you intuitively feel about your own conscious self. To me, this smells like a more abstract and philosophical version of the puddle analogy.
> "I" simply means "the person who is currently speaking"
But on this definition you can raise the question of why the person who is currently speaking is the person who is currently speaking (which by alternating de re and de dicto interpretations can be understood in the same non-tautologous ways as e.g. "Why is the person who is currently the President the person who is currently the President?") So this linguistic analysis doesn't succeed in dissolving facts about personal identity into nothing. You still have the fact that you are who you are and not someone else. And the intuitive notion of personhood (on which your definition depends and which you haven't in any way reduced to physics) is intimately connected with the idea of a more-or-less uninterrupted stream of first-person conscious experience.
> I wouldn't attribute much to how you intuitively feel about your own conscious self.
If we set 'intuitive feelings' aside, then of course the whole problem of conscious experience disappears immediately.
> And the intuitive notion of personhood (on which your definition depends and which you haven't in any way reduced to physics) is intimately connected with the idea of a more-or-less uninterrupted stream of first-person conscious experience.
"person": a member of the genus Homo
"speaking": phenomenon wherein the previous object vibrates its own vocal chords and moves its own mouth to produce sound waves
"currently": a point in time in which the aforementioned act occurs
Notably missing are: any references to continuity of experience, conscious action, or even thought. Suggestion: I have, in fact, completely reduced it to physics.
> You still have the fact that you are who you are and not someone else
Please describe to me a hypothetical universe where that statement doesn't hold true. If there is none, then we must accept that this "fact" does not require any explanation, and therefore can be dismissed as trivial.
Your linguistic analysis of 'I' doesn't work if understood in purely physical terms. Lots of people are speaking at any given moment, but I don't refer to all of them if I say 'I'.
Consider the absurdity of the question “who am I?”, uttered by an amnesiac, if it means simply “Which lump of physical stuff is currently speaking?” Even if we ignore the problem mentioned in the first paragraph, the answer is trivial – the same lump that’s making the noises. But it’s difficult to accept that the amnesiac is confused over a triviality: they really don’t know who they are; they lack a key piece of non-trivial, non-tautologous knowledge.
>If there is none, then we must accept that this "fact" does not require any explanation
As I've tried to emphasise, I do not claim that the fact is puzzling or requires an explanation, only that it is a fact. By analogy, it is not puzzling that the sum of two and two is four, and no non-trivial explanation of this fact appears to be required, but it is still a fact. Now of course you can try to make such fact dissolve via various forms of philosophical therapy. For example, there are some philosophers of mathematics who would try to argue that all mathematical facts are tautologous. You are trying to do something similar with facts of personal identity. However, philosophers of mathematics who claim that all mathematical truths are disguised tautologies can point to lots of actual work that has been done to show that this position is more plausible than it might first appear.
> Consider the absurdity of the question “who am I?”, uttered by an amnesiac
In that context, that question would just mean "what was my life like prior to losing my memories?", wouldn't it? So in this instance, the missing non-trivial knowledge is their long-term memory, not a problem with understanding the definition of "I".
> For example, there are some philosophers of mathematics who would try to argue that all mathematical facts are tautologous. You are trying to do something similar with facts of personal identity.
I'm not arguing that the subjective experience of personal identity is tautologous, I'm arguing that it's a chemical reaction (EDIT: and that the underlying objective truth is tautologous). Any feeling about the intuitive concept of "myself" having some kind of esoteric component above the physical matter (which I also share, don't be mistaken) would, presumably, also be given voice to by a computer simulation of your brain. That would be your brain being caught red-handed in the act of lying to itself about how special it is. And if this turns out not to be the case, then we have rock solid evidence that something is indeed missing from our simulation, which gives us an opportunity to measure that something, which in turn makes that something physical.
> Your linguistic analysis of 'I' doesn't work if understood in purely physical terms. Lots of people are speaking at any given moment, but I don't refer to all of them if I say 'I'.
Valid point. Refinement: in any speech, "I" refers to the person making that speech.
If you are using an abstract definition of "yourself" (such as your brain's internal representation of you), you are no longer talking about physical objects, so of course your question can't be answered using physical facts alone. Similarly, "2+2=4" is a statement about our abstract representation of the world, not the real world itself. That we can reason about integers without relying on facts about the real world doesn't mean that integers are any more "real" than unicorns - or for that matter, your concept of "self".