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Re: "Identity" - is a modal notion

From: Henry Story <henry.story@bblfish.net>
Date: Thu, 1 Jun 2017 20:59:55 +0200
Message-Id: <E4F26AAE-6315-4D1B-92C3-D18D28201A86@bblfish.net>
Cc: public-credentials@w3.org
To: Steven Rowat <steven_rowat@sunshine.net>
Yes, it looks like Joe's definition is one of what makes a thing the thing it is.

> On 1 Jun 2017, at 20:08, Steven Rowat <steven_rowat@sunshine.net> wrote:
> On 2017-06-01 9:06 AM, Joe Andrieu wrote:
>>  Identity is innately
>> trans-system. Any given "digital identity" may not be, but our real
>> world "identity" absolutely is. By its very nature. We have an identity
>> completely independent of any system or authority.

This I suppose is behind Heraclitus statement that 
"You could not step twice into the same river."

It is also the old question of how much change one can make to something and it still 
be the same thing, as the old paradox of Theseus Ship makes clear 
https://www.wikiwand.com/en/Ship_of_Theseus <https://www.wikiwand.com/en/Ship_of_Theseus>

These are questions of the essence of things - or the essence of things under a description, 
as is made clear when one wonders what the relation between a statue and the clay it is
made of is. The clay statue can stop existing whilst the material it is made of continues to
exist. https://plato.stanford.edu/entries/material-constitution/ <https://plato.stanford.edu/entries/material-constitution/>

The same thing under a different concept can therefore have different identity criteria.
Saul Kripke in "Naming and necessity" gave a definition of the identity for a human being
as the process that starts from the same initial cause: namely the same sperm and egg meeting.
David Lewis later argued that this is what constitutes the cross world identity of an object: i.e. 
given that in different possible worlds different things will happen to you and me, in one I may be
rich in another poor. We know that across these worlds we have the same object because we can
locate the cross world identity of the initial cause and then trace the different possible paths that
entity traced across the space of possibilities.  Note that as a result of Kripke's definition of human
(and most animal identity) it necessary that we have the parents we do, even though it is a complete
chance event that produced us.

David Lewis somewhere argued that one could have other cross world identities for humans
that would lead to different essences. Eg. someone could choose mental state similarity as
one that should be used as personal identity, which would be better for making sense of the
statements of those who on a regular basis in Jerusalem identify with Christ.

Btw, both of those concepts can coexist: we just have different 4 dimensional objects that overlap
in parts.

Even though I think it is really worth keeping in mind these theories of identity, and they are needed to 
avoid falling into various philosophical/logical traps, it is perhaps not the topic that a credentials community
group needs to go in too much. Or if you do you can simply relegate this to the type of the object that you
are considering.  You could create a kripke type identity by stating that

_:x a kripke:Agent .

and you could identify the more pychological Lewisian agent  in the same document with 

_:y a lewis:Agent .

and if you are a government agency you could define your own criteria of identity that can be shorter than a whole persons
life with

_:z a us:Citizen .

or if you are playing a virtual reality game

_:oxo a Monster .

The type gives you the identity criteria to use to do cross world, cross time identity. 
Mereology here helps (the part of relation) so that you can say how one the sculpture is a
part of lumpal.

The next thing is out of all the kripke:Agents (or other type) do you identify one of the members
of that type. That you do by desribing the object with a definite description. 
https://plato.stanford.edu/entries/descriptions/ <https://plato.stanford.edu/entries/descriptions/>

i.e., the kripke:Agent who knows the private key of this public key, or the us:Citizen who has 
identity number x, and these other properties, etc...

There are various logical theories about this, some that are good at explaining human speech
(as David Lewis's does in his 1973 book Counterfactuals applied to description logics as I recently
rediscovered) or one that would work better for something such as the internet
where context cannot be determined the same way as in everyday 3d life.  

That is where the work on the semantic web and others helps since those are logics built
for the web. I pointed to WebID spec as an example of how one can identify an agent via a public key
indirectly. One could also identify an agent via an openid the same way or via the ownership of a home
page, or e-mail, etc. patterns which the foaf ontology have amply demonstrated.

Looks like this should be developed as part of my thesis.


> Henry Story wrote, a few hours before that:
>> My guess is that a lot of the tension is coming from the notion of there being one true identity,
>> whatever that means, whereas it is just a relation of a name to a thing.
> I believe Joe and Henry are talking past each other in a fundamental way that might be a good example of the tar-pit that Manu likes to talk of.
> Nonetheless, I've found Joe's statements refreshing, and I agree with almost all of them so far, so I'd like to take a stab at expressing how this 'talking past each other' is accomplished, in my view. It seems to me it might be an important difference.
> Henry's position (in my words, using Henry's terminology):
> I believe 'thing' in Henry's statement, "relation of a name to a thing" can be a real person, which is the most important type of example. So I'll discuss that case.
> Therefore Henry is saying that 'Identity' is the relation of one name (label) to a given person. So there can be many Identities for a person. Each name is a new identity. Or, perhaps he'd agree there can be subsets of labels, correlations of several labels to one person. But there's no superset of 'all' names (labels) for the person, that we can call 'identity'.
> Joe's position (in my words, using Henry's terminology)
> I believe Joe is most concerned with the fact that a given thing (person) is unique in the world. And that any collection of labels that relate to that person is part of an assumed superset relating to them, and "Identity" is the whole superset. How much of the superset we see at one time varies, but it exists because the person exists.
> So to Joe, "Identity" refers to the existence of a unique person, and any labels that refer to that person.
> To Henry, "Identity" refers to the existence of a unique label, or set of labels relating to a person.
> They seem to be focusing on different parts of the same relationship.
> How might this help the current deliberations? Not sure, but:
>  -- I believe that Joe's usage for "Identity" is closer to what the average of the 7 billion people on the planet would use, by a wide margin.
>  -- I believe Joe's usage would match an attempt to integrate, manage, and facilitate  digital<-->non-digital flows of goods and people and information better than the multiple-label use of "Identity".
>  --I believe Henry's usage is easier to set up in the short term, digitally, or within any single jurisdiction.
> Steven
Received on Thursday, 1 June 2017 19:00:41 UTC

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