Of course you aren’t explicitly trying to define One True Approximation, but I have the impression you’re looking for One True Answer without acknowledging that any answer is necessary an approximation (and therefore, as you say, it makes no sense to look for One True Approximation—that was part of my point).
What we need is to define practical useful approximation
I’m not sure that’s correct. If we’re looking at “exotic” situations with imperfect uploads, etc., then I think the intuitions we have built around the idea of “identity” are likely to be unhelpful and may be unfixably unhelpful; we would do better to try to express our concerns in terms that don’t involve the dubious notion of “identity”.
different types of identity
I think there are many other different types of identity: other different things we notice and care about, and that contribute to our decisions as to whether to treat A and B as “the same person”. Physical continuity. Physical similarity. Social continuity (if some people maintain social-media conversations which are with A at the start, with B at the end, and interpolate somehow in between, then they and we may be more inclined to think of A and B as “the same person”). Continuity and/or similarity of personality.
(I should maybe clarify what I mean by “continuity”, which is something like this: A and Z have continuity-of-foo if you can find intermediates A-B-C-...X—Y-Z where each pair of adjacent intermediates is closely separated in space, time, and whatever else affects our perception that they “could” be the same, and also each pair of adjacent intermediates is extremely similar as regards foo. This is different from similarity: A and Z might be quite different but still connected by very similar intermediates (e.g., one person aging and changing opinions etc. over time), or A and Z might be quite similar but there might not be any such continuous chain connecting them (e.g., parent and child with extremely similar personalities once mature).)
It is partly because there are so many different kinda-identity-like notions in play that I think we would generally do better to work out which notions we actually care about in any case and not call them “identity” except in “easy” cases where they all roughly coincide as they do in most ordinary everyday situations at present.
“Numerical identity” is not a name for either of the two types of “identity” you describe, nor for any of mine, nor for anything that is clearly specifiable for persons. You can only really talk about “numerical identity” when you already have a clear-cut way of saying whether A is the same object as B. Parfit, unless I am badly misremembering, does not really believe in numerical identity for persons, because he thinks many “are A and B the same person?” questions do not have well defined answers. I hold much the same position.
Incidentally:
from our last discussions I remember that you deny existence of consciousness in some way
I certainly would not say that I deny the existence of consciousness, but it wouldn’t surprise me to learn that I deny some other things that you would call the existence of consciousness :-). I.e., perhaps your definition of “consciousness” has things in it that I don’t believe in.
In fact while it may seems to look like that I am listing all possible solution to find one true one as mine mentioning of AIXI imply, it is not so.
I was going to dissolve intuitive notion of identity into elements and after use these elements to construct useful models. These model may be complex, and it may consists of many blocks, evolving over time and interacting.
But it is clear to me (if soul doesn’t exist) than there is no real identity. Identity is only useful construction, and I am free to update it depending of my needs and situation, or not use it at all.
The idea of identity is (was) useful to solve some practical tasks, but sometimes it makes these tasks more obscure.
Yes, numerical identity is not “consciousness identity”, it is about “exactly the same thing”.
Consciousness identity is answering question “what I will experience in the next moment of time”. There are a lot of people who claim that “exact copy of me is not me”.
I used the following “copy test” to check personal ideas about identity: “Would you agree to be instantly replaced by your copy?” many people say: “No, I will be dead, my copy is not me”.
Update: But there is one thought experiment that is very strongly argue against idea that identity is only a model. Imagine that I am attached to rails and expecting that in one hour a train will cut my leg.
If identity would be only a model I would be able to change it in a way that it will be not me in the next 60 minutes. I could think about millions very similar beings, about billion of my copies in the parallel worlds, about open identity and closed individualism. But I will not escape from rail.
My model of identity is in firmware of my brain, and results from long term evolutionary process.
Of course you aren’t explicitly trying to define One True Approximation, but I have the impression you’re looking for One True Answer without acknowledging that any answer is necessary an approximation (and therefore, as you say, it makes no sense to look for One True Approximation—that was part of my point).
I’m not sure that’s correct. If we’re looking at “exotic” situations with imperfect uploads, etc., then I think the intuitions we have built around the idea of “identity” are likely to be unhelpful and may be unfixably unhelpful; we would do better to try to express our concerns in terms that don’t involve the dubious notion of “identity”.
I think there are many other different types of identity: other different things we notice and care about, and that contribute to our decisions as to whether to treat A and B as “the same person”. Physical continuity. Physical similarity. Social continuity (if some people maintain social-media conversations which are with A at the start, with B at the end, and interpolate somehow in between, then they and we may be more inclined to think of A and B as “the same person”). Continuity and/or similarity of personality.
(I should maybe clarify what I mean by “continuity”, which is something like this: A and Z have continuity-of-foo if you can find intermediates A-B-C-...X—Y-Z where each pair of adjacent intermediates is closely separated in space, time, and whatever else affects our perception that they “could” be the same, and also each pair of adjacent intermediates is extremely similar as regards foo. This is different from similarity: A and Z might be quite different but still connected by very similar intermediates (e.g., one person aging and changing opinions etc. over time), or A and Z might be quite similar but there might not be any such continuous chain connecting them (e.g., parent and child with extremely similar personalities once mature).)
It is partly because there are so many different kinda-identity-like notions in play that I think we would generally do better to work out which notions we actually care about in any case and not call them “identity” except in “easy” cases where they all roughly coincide as they do in most ordinary everyday situations at present.
“Numerical identity” is not a name for either of the two types of “identity” you describe, nor for any of mine, nor for anything that is clearly specifiable for persons. You can only really talk about “numerical identity” when you already have a clear-cut way of saying whether A is the same object as B. Parfit, unless I am badly misremembering, does not really believe in numerical identity for persons, because he thinks many “are A and B the same person?” questions do not have well defined answers. I hold much the same position.
Incidentally:
I certainly would not say that I deny the existence of consciousness, but it wouldn’t surprise me to learn that I deny some other things that you would call the existence of consciousness :-). I.e., perhaps your definition of “consciousness” has things in it that I don’t believe in.
In fact while it may seems to look like that I am listing all possible solution to find one true one as mine mentioning of AIXI imply, it is not so.
I was going to dissolve intuitive notion of identity into elements and after use these elements to construct useful models. These model may be complex, and it may consists of many blocks, evolving over time and interacting.
But it is clear to me
(if soul doesn’t exist) than there is no real identity. Identity is only useful construction, and I am free to update it depending of my needs and situation, or not use it at all.The idea of identity is (was) useful to solve some practical tasks, but sometimes it makes these tasks more obscure.
Yes, numerical identity is not “consciousness identity”, it is about “exactly the same thing”.
Consciousness identity is answering question “what I will experience in the next moment of time”. There are a lot of people who claim that “exact copy of me is not me”.
I used the following “copy test” to check personal ideas about identity: “Would you agree to be instantly replaced by your copy?” many people say: “No, I will be dead, my copy is not me”.
Update: But there is one thought experiment that is very strongly argue against idea that identity is only a model. Imagine that I am attached to rails and expecting that in one hour a train will cut my leg.
If identity would be only a model I would be able to change it in a way that it will be not me in the next 60 minutes. I could think about millions very similar beings, about billion of my copies in the parallel worlds, about open identity and closed individualism. But I will not escape from rail.
My model of identity is in firmware of my brain, and results from long term evolutionary process.