Deutsch on SSA
Dear Russel Do you have any comment to this comment by Deutsch on another list about these matters? Regards Lennart - Original Message - From: David Deutsch [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, October 31, 2003 3:07 PM Subject: Re: The Turing Principle and the SSA On 31 Oct 2003, at 4:59 am, Brian Scurfield wrote: First, I think we should be careful to distinguish the Self-Sampling Assumption (SSA) from the Strong Self-Sampling Assumption (SSSA). SSA: One should reason as if one were a random sample from the set of all observers in one's reference class. SSSA: Each observer-moment should reason as if it were randomly selected from its reference class. One problem with both of these is that there is no preferred meaning to sampling *randomly* from an infinite set, except in certain very special cases. A discrete infinity of copies of me is not one of those cases, so I don't think it is meaningful to select randomly from the set of all observers who will ever be created who are (in any sense) like me. So doesn't the thing fall down at the first hurdle? -- David Deutsch - Original Message - From: Russell Standish [EMAIL PROTECTED] To: Saibal Mitra [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Sent: Sunday, November 02, 2003 5:45 AM Subject: Re: Quantum accident survivor I disagree. You can only get an effect like this if the RSSA is invalid. You've been on this list long enough to remember the big debates about RSSA vs ASSA. I believe the ASSA is actually contrary to experience - but never mind - in order to get the effect you want you would need an SSA that is neither RSSA nor ASSA, but something *much* weirder. Cheers Saibal Mitra wrote: There have been many replies to this. I would say that you wouldn't expect to survive such accidents. Assume that we are sampled from a probability distribution over a set of possible states. E.g. in eternal inflation theories all possible quantum states the observable universe can be in are all realized, so all possible situations you can be in, do occur with some finite probability. In such theories you ''always'' exist. But this doesn't mean that if you are Mohammed Atta saying your prayer just before impact with the WTC, your next experience is that the plane has tunneled through the WTC without doing any harm. This is because there are many more Mohammed Attas in the universe that do not have this experience. So, you would ''survive'', but in a different branch with memory loss plus some aditional ''false'' memories. In that branch you wouldn't have been in that plane to begin with. You should think of yourself at any time as if you were chosen by a random generator sampled from a fixed probability distribution over the set of all possible states you can be in. The state that corresponds to you have experienced flying through the WTC is assigned an extremely small probability. How does this square with the normal experience of continuity through time? Well, every ''observer moment'' as chosen by the random generator has a memory of past experiences. So, if you go to bed now and wake up the next morning, you have the feeling of continuity, but this is only because the person waking up has the memory of going to bed. You could just as well say that the person going to bed survives in any one of the possible states he can be in. The state that happens to have the memory of going to bed is just one of these possible states. That particular state has the illusion of being the continuation of the first state. Oorspronkelijk bericht - Van: David Kwinter [EMAIL PROTECTED] Aan: [EMAIL PROTECTED] Verzonden: Friday, October 31, 2003 02:58 AM Onderwerp: Quantum accident survivor Another quickie: Assume I survive a car/plane crash which we assume could have many different quantum outcomes including me (dead || alive) Since I was the same person (entire life history) up until the crash/quantum 'branch' - then can't I assume that since there was at least one outcome where I survived, that TO ME I will always survive other such life/death branches? Furthermore if I witness a crash where someone dies can I assume that the victim will survive in their own world so far as at least one quantum branch of survivability seems possible? David Kwinter -- -- A/Prof Russell StandishDirector High Performance Computing Support Unit, Phone 9385 6967, 8308 3119 (mobile) UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119 () Australia[EMAIL PROTECTED] Room 2075, Red Centre http://parallel.hpc.unsw.edu.au/rks International prefix +612, Interstate prefix 02 -- --
Re: Deutsch on SSA
David Deutsch wrote about the Self Selection Assumption, on the Fabric-of-Reality list: One problem with both of these is that there is no preferred meaning to sampling *randomly* from an infinite set, except in certain very special cases. A discrete infinity of copies of me is not one of those cases, so I don't think it is meaningful to select randomly from the set of all observers who will ever be created who are (in any sense) like me. So doesn't the thing fall down at the first hurdle? First, I'm not so sure it is true that you can't select randomly from an infinite set. In the level 1 multiverse, there are an infinite number of copies of me. On some philosophical perspectives, I am exactly one of those copies. This represents an actual choice from an infinite set. Anyone who accepts both of these principles (the level 1 multiverse and the fact that he is actually in a single location) must accept the possibility of random selection from an infinite set. But suppose we do accept that this is impossible. The SSA could still work if it turned out that there were only a finite number of observers and observer-moments in the reference class. This is plausible if two conditions hold. The first is that each observer is described by only a finite amount of information. This is established by our current theories of physics. The second is that there is an upper limit on the size an observer could have; that is, that there are no infinitely or arbitrarily large observers. That is a little harder to defend, but for an observer of arbitrary size to come about, the universe (its universe, that is) would have to last subjectively forever, and have an infinite amount of information in it. Therefore I think it is rather problematic to suppose that there is no upper limit on the size of an observer, as it requires infinities to creep into the physics of the universe in several places. If observers do have an upper limit, then there are only a finite number of possible observers, and possible observer-moments, and Deutsch's objection fails on that basis. Hal Finney
Re: Deutsch on SSA
I unsubscribed for the FOR list about 6 months ago, as I found I could
no longer put up with the dross on that list (not that DD is dross, of
course!).
I must admit, I'm not entirely sure what problem DD is alluding to
here. In order to apply the SSA requires a measure on the reference
class. Perhaps he is commenting that there is often no preferred
measure.
In the case of the RSSA, the measure is uniquely defined by the
Schroedinger wavefunction. In the case of ASSA, an absolute measure is
assumed to exist.
For me, a bigger problem with the SSA, and with Anthropic arguments
generally, is that the reference class is ambiguous.
Cheers
Lennart Nilsson wrote:
Dear Russel
Do you have any comment to this comment by Deutsch on another list about
these matters?
Regards
Lennart
- Original Message -
From: David Deutsch [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Friday, October 31, 2003 3:07 PM
Subject: Re: The Turing Principle and the SSA
On 31 Oct 2003, at 4:59 am, Brian Scurfield wrote:
First, I think we should be careful to distinguish the Self-Sampling
Assumption (SSA) from the Strong Self-Sampling Assumption (SSSA).
SSA: One should reason as if one were a random sample from the set of
all observers in one's reference class.
SSSA: Each observer-moment should reason as if it were randomly
selected from its reference class.
One problem with both of these is that there is no preferred meaning to
sampling *randomly* from an infinite set, except in certain very
special cases.
A discrete infinity of copies of me is not one of those cases, so I
don't think it is meaningful to select randomly from the set of all
observers who will ever be created who are (in any sense) like me. So
doesn't the thing fall down at the first hurdle?
-- David Deutsch
- Original Message -
From: Russell Standish [EMAIL PROTECTED]
To: Saibal Mitra [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]
Sent: Sunday, November 02, 2003 5:45 AM
Subject: Re: Quantum accident survivor
I disagree. You can only get an effect like this if the RSSA is
invalid. You've been on this list long enough to remember the big
debates about RSSA vs ASSA. I believe the ASSA is actually contrary to
experience - but never mind - in order to get the effect you want you
would need an SSA that is neither RSSA nor ASSA, but something *much*
weirder.
Cheers
Saibal Mitra wrote:
There have been many replies to this. I would say that you wouldn't
expect
to survive such accidents.
Assume that we are sampled from a probability distribution over a set of
possible states. E.g. in eternal inflation theories all possible quantum
states the observable universe can be in are all realized, so all
possible
situations you can be in, do occur with some finite probability. In such
theories you ''always'' exist.
But this doesn't mean that if you are Mohammed Atta saying your prayer
just
before impact with the WTC, your next experience is that the plane has
tunneled through the WTC without doing any harm. This is because there
are
many more Mohammed Attas in the universe that do not have this
experience.
So, you would ''survive'', but in a different branch with memory loss
plus
some aditional ''false'' memories. In that branch you wouldn't have been
in
that plane to begin with.
You should think of yourself at any time as if you were chosen by a
random
generator sampled from a fixed probability distribution over the set of
all
possible states you can be in. The state that corresponds to you have
experienced flying through the WTC is assigned an extremely small
probability.
How does this square with the normal experience of continuity through
time?
Well, every ''observer moment'' as chosen by the random generator has a
memory of past experiences. So, if you go to bed now and wake up the
next
morning, you have the feeling of continuity, but this is only because
the
person waking up has the memory of going to bed.
You could just as well say that the person going to bed survives in any
one
of the possible states he can be in. The state that happens to have the
memory of going to bed is just one of these possible states. That
particular
state has the illusion of being the continuation of the first state.
Oorspronkelijk bericht -
Van: David Kwinter [EMAIL PROTECTED]
Aan: [EMAIL PROTECTED]
Verzonden: Friday, October 31, 2003 02:58 AM
Onderwerp: Quantum accident survivor
Another quickie:
Assume I survive a car/plane crash which we assume could have many
different quantum outcomes including me (dead || alive)
Since I was the same person (entire life history) up until the
crash/quantum 'branch' - then can't I assume that since there was at
least one outcome
Re: Deutsch on SSA
I think a related point is touched on in my paper Complexity and Emergence, as in Why Occam's razor. In both of these cases, one is selecting from an infinite discrete set (of descriptions), which have a uniform measure associated with them. The answer you get, is the the probability of selection is related in a simple way to the complexity of the description, as perceived by the observer. There are no paradoxes, but the results are observer dependent in a way that makes a lot of scientists uncomfortable. Cheers Hal Finney wrote: David Deutsch wrote about the Self Selection Assumption, on the Fabric-of-Reality list: One problem with both of these is that there is no preferred meaning to sampling *randomly* from an infinite set, except in certain very special cases. A discrete infinity of copies of me is not one of those cases, so I don't think it is meaningful to select randomly from the set of all observers who will ever be created who are (in any sense) like me. So doesn't the thing fall down at the first hurdle? First, I'm not so sure it is true that you can't select randomly from an infinite set. In the level 1 multiverse, there are an infinite number of copies of me. On some philosophical perspectives, I am exactly one of those copies. This represents an actual choice from an infinite set. Anyone who accepts both of these principles (the level 1 multiverse and the fact that he is actually in a single location) must accept the possibility of random selection from an infinite set. But suppose we do accept that this is impossible. The SSA could still work if it turned out that there were only a finite number of observers and observer-moments in the reference class. This is plausible if two conditions hold. The first is that each observer is described by only a finite amount of information. This is established by our current theories of physics. The second is that there is an upper limit on the size an observer could have; that is, that there are no infinitely or arbitrarily large observers. That is a little harder to defend, but for an observer of arbitrary size to come about, the universe (its universe, that is) would have to last subjectively forever, and have an infinite amount of information in it. Therefore I think it is rather problematic to suppose that there is no upper limit on the size of an observer, as it requires infinities to creep into the physics of the universe in several places. If observers do have an upper limit, then there are only a finite number of possible observers, and possible observer-moments, and Deutsch's objection fails on that basis. Hal Finney A/Prof Russell Standish Director High Performance Computing Support Unit, Phone 9385 6967, 8308 3119 (mobile) UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119 () Australia[EMAIL PROTECTED] Room 2075, Red Centrehttp://parallel.hpc.unsw.edu.au/rks International prefix +612, Interstate prefix 02
