Re: More on identifiers

From: Brian Selzer <>
Date: Fri, 5 Jun 2009 16:25:23 -0400
Message-ID: <OafWl.31155$>

"Walter Mitty" <> wrote in message news:oC9Wl.801$
> <> wrote in message
> On Jun 5, 1:25 pm, "Walter Mitty" <> wrote:
>>> Consider two electrons. They both have the same mass, and they have the
>>> same charge. They might have opposite spins. But the minute we add a
>>> third
>>> electron, the spin of two of them is going to be identical. It seems
>>> that,
>>> on the surface at least, electrons do not have enough properties to
>>> carry
>>> identity.
>>If objects are really not distinguishable then why someone would want
>>to artificially identify them? Wouldn't be better to record just their
> Good point. So there are some case where identity is not important.
> (Incidentally, the other response where the comment was made that two
> electrons must occupy different states leads to a slippery slope. Using
> state to identify implies that a change of state is in effect a change of
> identity. This is related to Brian's claim that all attributes of an
> entity are mutable. (Am I misinterpreting your claim, Brian?)

I'm not sure.

For ordinary things--that is, for things that have a locus in time--identity requires that every property exemplified at every location in time be the same. It doesn't require that every property be the same at every location in time. If someone asserts that at exactly 12:31, the guy that was in second in line at exactly 12:30 is now first in line, then it is reasonable to conclude that if you're referring to the guy that was second in line at exactly 12:30, then you're referring to the guy that was first in line at exactly 12:31.

What I think you're referring to as my claim is that it is possible for every component of a pair of tuples that map to a particular thing in the Universe at successive databases to be different. For example, there could be a plastic bin located somewhere in a warehouse with a label with "A12" on it on Friday, and that same plastic bin could be located somewhere else with a different label with "A14" on it on Monday. The fact that its location and label both changed doesn't mean that it isn't the same plastic bin. So here are the tuples at successive databases

before moving {Label:"A12",Location:R24S3}

after moving {Label:"A14",Location:R15S1}

Obviously, every component of the tuples are different, yet both map to the same plastic bin.

<snip> Received on Fri Jun 05 2009 - 22:25:23 CEST

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