From newshub.ccs.yorku.ca!ists!helios.physics.utoronto.ca!news-server.ecf!utgpu!cs.utexas.edu!uunet!mcsun!uknet!edcastle!aiai!jeff Mon May 25 14:04:52 EDT 1992
Article 5594 of comp.ai.philosophy:
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>From: jeff@aiai.ed.ac.uk (Jeff Dalton)
Newsgroups: comp.ai.philosophy
Subject: Re: Systems Reply I (repost perhaps)
Message-ID: <6700@skye.ed.ac.uk>
Date: 12 May 92 19:56:38 GMT
References: <6684@skye.ed.ac.uk> <1992May10.162915.23987@ccu.umanitoba.ca> <1992May11.065930.10848@psych.toronto.edu>
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In article <1992May11.065930.10848@psych.toronto.edu> christo@psych.toronto.edu (Christopher Green) writes:
>In article <1992May10.162915.23987@ccu.umanitoba.ca> zirdum@ccu.umanitoba.ca (Antun Zirdum) writes:
>>In article <6684@skye.ed.ac.uk> jeff@aiai.ed.ac.uk (Jeff Dalton) writes:
>>[stuff about Understanding]
>>>
>>>No I don't.  I can _conclude_ that it's not present.  Like this:
>>>
>>>   1. Computers can't understand.
>>>   2. Mechanims M is necessary for understanding.
>>>   3. Therefore computers lack M.
>>>
>>Hey, why not! Circular reasoning always works for me!
>>(Computers can't understand, because they can't
>>understand.)
>>	This is no argument at all.
>
>Get your fallacies right. This isn't circular, but it is a case of the 
>fallacy of denying the antecedent:
>
>~U
>U->M
>---
>~M
>
>If premise 2 were changed to: "Mechansims M are sufficient for understanding"
>then the argument would be a perfectly valid modus tollens:
>
>~U
>M->U
>---
>~M
>
>Logic Rules! :-)

Just so.  I did notice this when writing a reply I posted earlier
today.  I _meant_ to use a modus tollens, but I was careless and
probably was confused by the similar arguments designed to show
humans had the properties necessary for understanding (if we agree
humans can understand).  Indeed, I can remember thinking after
I'd written those articles that I had a "not" wrong somewhere.
Now I hope this was the only one...

Thanks, BTW, for pointing out the correct form of the argument
rather than saying what an idiot that Dalton must be.

-- jeff


