# Re: A pk is *both* a physical and a logical object.

Date: Thu, 19 Jul 2007 13:07:37 -0300
Message-ID: <469f8c23\$0\$8838\$9a566e8b_at_news.aliant.net>

> On 13 jul, 16:54, "Brian Selzer" <br..._at_selzer-software.com> wrote:
>

```>>"Jan Hidders" <hidd..._at_gmail.com> wrote in message
>>
>>
>>
>>
>>
>>>On 13 jul, 06:17, "Brian Selzer" <br..._at_selzer-software.com> wrote:
>>
>>>>I was thinking more along the lines of the difference between what can be
>>>>and what can be true.
>>
>>>Very little, I imagine. :-)
>>
>>{a, b, c} is different from {{a}, {b}, {c}}, yes?  A description of the
>>universe is a description of what can be.  What can be true is a description
>>of a description of what can be.
```

>
>
> I don't see a distinction between "can be" and "can be true", for me
> those are synonymous. Perhaps you meant "is" and "can be"? Note that
> the UoD is anything you might want to talk about, and therefore
> usually describes what "can be" and not just "what is".
>
>
```>>>So you meant static constraints? Why do you think those would not be
>>>part of the description of the UoD?
>>
>>I was thinking more along the lines of relation schemata, which can be
>>represented either by open sentences in first order logic (which if included
>>as part of the description of the universe would mean that that description
>>is incomplete) or by contingent sentences in quantified modal logic.  In
>>either case an assignment is required to obtain what is actually true about
>>their referents, and by extension, about the universe.
```

>
>
> Why restrict yourself only to those logics? Anyway, all that is part
> of the UoD.
>
>
```>>So, at the logical level, you describe not only the Universe of Discourse,
>>but also what can be said about the Universe of Discourse.
```

>
>
> That is by definition also part of the UoD.
>
> -- Jan Hidders

The UoD can also contain what cannot be. How can we discuss what cannot be unless it is in our universe of discourse? Received on Thu Jul 19 2007 - 18:07:37 CEST

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