X-Message-Number: 20933
From: 
Date: Tue, 21 Jan 2003 11:08:14 EST
Subject: clarify?

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I think this will be my last try, for now at least, on clarifying "identity" 
of "indiscernibles."

Am I totally senile, or is Michael Price (along with many others) missing the 
point?

1. He writes that "same" does not mean "identical," and his example is that 
he might have eaten the "same" (kind of) food today as yesterday, but it 
wouldn't "identical" (recycled). It appears to me he is pleading guilty to my 
charge of inventing his own lexicon (along with his colleagues). If your menu 
today was exactly the same as yesterday, surely many or most people would 
indeed agree they had eaten identical food. That is simply the way the word 
is commonly used. Of course technical jargon is often permitted its own 
meaning, even when common words are used, but this is a bad habit. If you use 
common words, you should use them with traditional meanings. 

If anyone doubts that scientists can have bad habits, there are many 
examples. One that ought to be striking is the use of "dimensions" for units 
of measure. FD (force times distance) can mean either work (energy) or torque 
(if "distance" is interpreted to mean "lever arm"). So a foot-pound, or a 
pound-foot, can be either work or torque, even though these are very 
different. Shape up, guys! 

2. He also writes:

>Granted, you can distinguish between them [electrons at different 
locations], but they are, nevertheless,
>identical and (by QED) continuously swapping identities.

So now "indiscernible" does not mean "indistinguishable," but rather 
"indistinguishable except for location and anything else that my experiments 
to date have not revealed." 

Also,  "continuously swapping identities" is a strange way to express 
oneself, if you believe the objects are "identical" to begin with. How can 
they change or swap identities if they have the same identity all along? 
Granted, you could write a long, clumsy explanation as to what you mean, but 
why is that necessary or useful? What purpose does it serve? Why not just 
state the objective facts--that such and such an experiment yields such and 
such a result--and let it go at that?

3. >Extra internal particle complexity (i.e. attributes) that
>would distinguish same-type-particles from each other is forbidden.  The
>possibility of extra distinguishing attributes is "absolutely forbidden"
>between particles that have demonstrated quantum interference. 

New complexity has certainly been discovered since the beginnings of quantum 
theory. Spin, quarks, whatnot, and lots of new possibilities including extra 
dimensions. Surely it must be clear that "absolutely forbidden" means IN THE 
CONTEXT of current theory and experiment. Naturally, I have no quarrel with 
the assertion that current quantum theory, since it has been so successful, 
must have considerable truth in it within rather broad limits, but that was 
true of Newtonian physics also.

4. It's redundant, but he also writes:

>"The occurrence of the Pauli exclusion or the formation of Bose-Einstein
>condensates (both forms of quantum interference between identical
>objects) demonstrates that the entanglements [and gravitational effects]
>you speak of are irrelevant to the question of identity."

Irrelevant only if you previously DEFINE "identity" by the quantum 
interference criterion. The whole point is to prevent language from 
distorting science or misleading us.

Finally, for most readers here, the important question is the relevance of 
these matters to personal survival criteria, and the answer is that we don't 
know yet, no matter how loudly or focefully some may press their views. It 
can plausibly be argued that "you" share "identity" with a duplicate, or an 
emulation, or a predecessor, or a continuer; and in each case an opposing 
argument can be made, with striking thought experiments. My own tentative 
view is that it is a quantitative question, and related to the duration of 
the objective and subjective present. In any case, most of us agree that the  
rational thing to do is (1) try to live a little longer, and (2) arrange for 
cryopreservation in case you absent-mindedly die a little too soon.

Robert Ettinger



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