Mark Peaty writes:

SP: 'Is there anything about how you are feeling to day that makes you sure 
that aliens didn't come during the night and replace your body with an exact 
copy? Because that is basically what happens naturally anyway, although it 
isn't aliens and it takes months rather than overnight: almost every atom in 
your body is replaced with another atom, put in roughly the same place. If the 
discarded atoms were kept rather than sloughed off, exhaled etc. you would see 
that your identical twin of a few months ago had died and no-one even noticed, 
because it happened gradually. Other than in the speed and scheduling of your 
death, how does destructive teleportation differ from normal life?'
 *   I know, which here means 'believe with confidence', that aliens didn't 
come because everything feels, looks, smells, etc, as normal. I am a creature 
of habit just like you and there is no evidence of radical differences anywhere 
that I can notice.

That's the point, and the point of the chapters in Parfit's "Reasons and 
Persons" about personal identity. I would have bet that you would agree given what 
you said about consciousness being entirely bases on the physical structure of your body: 
if the physical structure is preserved, how would you know your body had been replaced? 
Of course if the aliens left you with antennas coming out of your head or made you forget 
that you were married you or someone else would quickly notice, but how is it even 
possible that such a change could occur as a result of the duplication if the duplication 
is of the engineering tolerance is at least as good as that of a normal overnight sleep?

 *   I quibble about whether atoms are replaced within DNA except as part of 
the normal processes of replication and repair. That aside, it is not the atoms 
per se which gives my identity but their incorporation into molecular 
structures, and the incorporation of all these molecular structures 
holonistically into cells, organs, and all the rest. Our bodies are held 
against collapse smallwards by the robust durability of genetic structures 
which embody all the patterns needed to sustain our biological integrity 
against the entropy within the flow of energy and resources through our 
ecological niches. Mental integrity is maintained in analogous manner by means 
of the robust durability of meme structures embodied in neural networks and 
whatever emergent super-neural structures they entail.

Atoms are replaced in DNA as well as neurons. There is the passive replacement mechanism 
whereby chemicals in solution exchange atoms with their environment, and more gross 
changes where the structural integrity of important macromolecules is compromised and 
either is repaired by specific mechanisms or the cell dies (eg. look up "DNA 
repair" in Wikipedia). In any case, even if this were not so and the DNA molecule 
were kept in some sort of protective case and read off with a laser beam so that it was 
never sullied by direct contact with the environment, what difference would it make if 
every such protected molecule were replaced with an exact copy? An atom is an atom: the 
hydrogen atoms in your body are the same as each other and the same as the hydrogen atoms 
in interstellar space.

 *   Destructive teleportation differs from normal life in that it entails the 
[as yet unlawful] killing of a person whose body is dismembered  in a very high 
resolution process during the course of a magical ceremony, after which there 
soon arrives postcards and news from a person in a faraway place claiming to be 
the deceased and wanting access to his/her money box. The police and other 
authorities in that far away place, when asked and paid, will provide evidence 
that the healthy body of the person who turned up there during a magical 
ceremony matches the fingerprint, DNA and polygraph signatures of the deceased. 
They will also report that she/he is suffering from culture shock, but 
otherwise seems OK. All of these facts point to our day to day experience of 
survival being very much a social and cultural construct in which we believe, 
no more and no less.

What matters in survival is that you remain you, just as you do in the course 
of normal life. What happens in the course of normal life is that gradually 
aimost all the atoms in your body are replaced. If they were not lost, but 
collected where they fell and their relative arrangement to each other 
maintained, there would be at least one copy of you thus collected every few 
months to years. This copy normally disintegrates, so you don't notice his 
death. The main difference between normal life and what we have been calling 
destructive teleportation (apart from the spatial displacement, which is why I 
made the aliens duplicate you in your bed) is that in the latter, it happens 
quickly and is supposed to be much more exact. And why should it make any 
difference to you if it is revealed that the atoms of your body were replaced 
all at once or gradually over time? How would you react if your wife shunned 
you because you are not, literally, the man she married but only an approximate 
copy who believes he is the same man?

 *   It therefore seems apparent that problems and conundrums raised by the 
destructive teleporter/biofax machines are based understood by recognising that 
our experience of being here now and seeming to be the same person from day to 
day, indeed from moment to moment, is what it is like to be a description of a 
person, although I would say that the qualia aspect is actually what it is like 
to be the updating of the description. It was ever thus.

That's right - and the experience of living your life from day to day would not 
be disrupted by destructive teleportation. Non-destructive teleportation, or if 
the atoms in your body a year ago were kept and their relative positions 
maintained, would be a different matter.

Stathis Papaioannou
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