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Re: major problem with diff:replacement: continued

From: Henry Story <henry.story@bblfish.net>
Date: Sat, 15 May 2004 13:11:55 +0200
Message-Id: <ACB52A3E-A660-11D8-B1B4-000A95D9FA7A@bblfish.net>
To: public-cwm-talk@w3.org

I think diff:replace moves us into the domain of modal logic, as 
explained for example by David Lewis in his book Counterfactuals.

The problem with a replacement of a fact is that you can rarely just 
replace on fact in a theory. Replacing a fact entails all kinds of 
other changes. So consider:

If I had not paid my bill I would have been in trouble.

The actual world here is the one where I do pay my bill.
We are asked in the actual world to consider what would have happened 
had I not paid my bill.
we are doing something like

{pay my bill} diff:replace {}

But the world where I don't pay my bill, is also a world where I have 
more money, where I could have spent money that evening, that might 
have allowed me to meet someone who could have changed my life, etc. 
etc.

These are all points made by David Lewis in the introduction to his 
book.

A little pause.

Henry



On 15 May 2004, at 12:42, Henry Story wrote:
>
> Before continuing let me check that this mailing list accepts image 
> attachments.
Received on Saturday, 15 May 2004 07:12:01 GMT

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