âIf youâre entirely a physicalist and believe in computational theory of mind, what reason is there for you not to believe you could recreate a persons consciousness? Just exactly replicate all their brain processes.â This is confusing 2 different kinds of identity, âqualitativeâ and ânumericalâ. :
Qualitative identity=I can have 2 different (qualitatively) identical apples, if one is a perfect duplicate of the other
Numerical identity=X is numerically identical to Y, if theyâre the same object, for example âthe morning starâ and âthe evening starâ are numerically identical, since these are both old names for the planet Venus.
What physicalism implies is that if you build someone who has all the same physical properties as me then they will be qualitatively identical to me, full-stop, because physicalism just is the view that all properties of things are fixed by their physical properties. But that doesnât automatically mean theyâd be numerically identical to me, any more than if I create a perfect duplicate of an apple, their both the same apple. Common-sense says âno they are not the same apple, because I started with only one apple and now I have 2, and if there are 2 apples, they are (numerically) distinct from each otherâ. You could of course have a theory that âsame personâ is special, in that any perfect duplicate of me just is me. But I donât think that is very plausible: build a perfect duplicate of me while I am alive, and it seems like you have two (qualitatively) identical people, not just one person who is somehow in 2 places at once.
I think some people are confused about this because theyâve heard philosophers have âpsychologicalâ theories of personal identity, where if the informational contents of your brain get wiped and moved to another new brain, then you are the person with the new brain. But actually, the theories that philosophers take seriously which imply this donât say that if two people have exactly the same mental properties, they must be the same person. What they say is that if thereâs a future person whoâs psychological state depends on your current state in the right way, then that future person is you*, and they then combined this with the idea that if info is deliberately transferred from your brain to another brain, this is a connection of the right sort for the person with the new brain to count as you.
*Actually, itâs a little more complicated than that: you need to add a clause saying âand no other person at the same point in the future has mental states that depend on yours in the right wayâ. Canât have 2 future people who are identical to you but not each other. Thatâs the key insight behind Derek Parfitâs famous argument that there are situations as selfishly good as survival for you but where you cease to exist: this happens when there are multiple duplicates of you whose mental states are each connected to yours in the right way.
âIf youâre entirely a physicalist and believe in computational theory of mind, what reason is there for you not to believe you could recreate a persons consciousness? Just exactly replicate all their brain processes.â This is confusing 2 different kinds of identity, âqualitativeâ and ânumericalâ. :
Qualitative identity=I can have 2 different (qualitatively) identical apples, if one is a perfect duplicate of the other
Numerical identity=X is numerically identical to Y, if theyâre the same object, for example âthe morning starâ and âthe evening starâ are numerically identical, since these are both old names for the planet Venus.
What physicalism implies is that if you build someone who has all the same physical properties as me then they will be qualitatively identical to me, full-stop, because physicalism just is the view that all properties of things are fixed by their physical properties. But that doesnât automatically mean theyâd be numerically identical to me, any more than if I create a perfect duplicate of an apple, their both the same apple. Common-sense says âno they are not the same apple, because I started with only one apple and now I have 2, and if there are 2 apples, they are (numerically) distinct from each otherâ. You could of course have a theory that âsame personâ is special, in that any perfect duplicate of me just is me. But I donât think that is very plausible: build a perfect duplicate of me while I am alive, and it seems like you have two (qualitatively) identical people, not just one person who is somehow in 2 places at once.
I think some people are confused about this because theyâve heard philosophers have âpsychologicalâ theories of personal identity, where if the informational contents of your brain get wiped and moved to another new brain, then you are the person with the new brain. But actually, the theories that philosophers take seriously which imply this donât say that if two people have exactly the same mental properties, they must be the same person. What they say is that if thereâs a future person whoâs psychological state depends on your current state in the right way, then that future person is you*, and they then combined this with the idea that if info is deliberately transferred from your brain to another brain, this is a connection of the right sort for the person with the new brain to count as you.
*Actually, itâs a little more complicated than that: you need to add a clause saying âand no other person at the same point in the future has mental states that depend on yours in the right wayâ. Canât have 2 future people who are identical to you but not each other. Thatâs the key insight behind Derek Parfitâs famous argument that there are situations as selfishly good as survival for you but where you cease to exist: this happens when there are multiple duplicates of you whose mental states are each connected to yours in the right way.