Philosophy is often presented as a rather useless, if perhaps interesting, type of thought.  Arguably, however, defective philosophies of mind are a leading cause of death today!  Exhibit one, Bryan Caplan:

What disturbed me was when I realized how low he set his threshold for [cryonics] success.  Robin didn’t care about biological survival.  He didn’t need his brain implanted in a cloned body.  He just wanted his neurons preserved well enough to “upload himself” into a computer.  To my mind, it was ridiculously easy to prove that “uploading yourself” isn’t life extension.  “An upload is merely a simulation.  It wouldn’t be you,” I remarked.  …

“Suppose we uploaded you while you were still alive.  Are you saying that if someone blew your biological head off with a shotgun, you’d still be alive?!” Robin didn’t even blink: “I’d say that I just got smaller.” … I’d like to think that Robin’s an outlier among cryonics advocates, but in my experience, he’s perfectly typical.  Fascination with technology crowds out not just philosophy of mind, but common sense.

Bryan, you are the sum of your parts and their relations.  We know where you are and what you are made of; you are in your head, and you are made out of the signals that your brain cells send each other.  Humans evolved to think differently about minds versus other stuff, and while that is a useful category of thought, really we can see that minds are made out of the same parts, just arranged differently.  Yes, you “feel,” but that just tells you that stuff feels, it doesn’t say you are made of anything besides the stuff you see around and inside you.

The parts you are made of are constantly being swapped for those in the world around you, and we can even send in unusual parts, like odd isotopes.  You usually don’t notice the difference when your parts are swapped, because your mind was not designed to notice most changes; your mind was only designed to notice a few changes, such as new outside sights and sounds and internal signals.  Yes you can feel some changed parts, such as certain drugs, but we see that those change how your cells talk to each other.  (For some kinds of parts, such as electrons, there really is no sense in which you contain different elections.  All electrons are a pattern in the very same electron field.)

We could change your parts even more radically and your mind would still not notice.  As long as the new parts sent the same signals to each other, preserving the patterns your mind was designed to notice, why should you care about this change any more than the other changes you now don’t notice?  Perhaps minds could be built that are very sensitive to their parts, but you are not one of them; you are built not to notice or care about most of your part details.

Your mind is huge, composed of many many parts.  It is even composed of two halves, your right and left brain, which would continue to feel separately if we broke their connection. Both halves would also feel they are you.  It is an illusion that there is only “one” of you in your head that feels; all your mind parts feel, and synchronize their feelings to create your useful illusion of being singular.  We might be able to add even more synchronized parts and have you still feel singular.

We could also completely stop cell signaling in your mind, and then start it up again, and you would have no memory of feelings of that time.   Afterward, you would still think you were the same you, because your head would have saved all the info needed to start your brain cells talking to each other again.  If we instead moved that info to a new set of parts that then talked to each other the same way, why should you care?  You will still feel, just as you feel when we leave your parts alone, because you never feel your parts!  You have never felt anything other than the signals sent between your cells.  So what could possibly make these new parts only a “simulation,” and your current parts the “real” you?

What if we moved your info into two different sets of parts?  You could declare one to be the “real” you via some arbitrary definition like the one closest in space to where you were before.  But each of them would feel like they were you, as much as you feel like yesterday’s you, and more than your two disconnected brain halves would feel they are you.  If tightly linked, these two new you might feel singular, like the two halves of your brain do now.

We have taken apart people like you Bryan, and seen what they are made of.  We don’t understand the detailed significance of all signals your brain cells send each other, but we are pretty sure that is all that is going on in your head.  There is no mysterious other stuff there.  And even if we found such other stuff, it would still just be more stuff that could send signals to and from the stuff we see.  You’d still just be feeling the signals sent, because that is the kind of mind you are.

Accept it and grab a precious chance to live longer, or reject it and die.  Consider: if your “common sense” had been better trained via a hard science education, you’d be less likely to find this all “obviously” wrong.  What does that tell you about how much you can trust your initial intuitions?

Added: Tyler giggles and Bryan responds.