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From: kube@cogsci.berkeley.edu (Paul Kube)
Newsgroups: sci.philosophy.tech
Subject: Re: Simplicity and truth (was: Re: Science and Aesthetics)
Message-ID: <20271@ucbvax.BERKELEY.EDU>
Date: Mon, 24-Aug-87 12:43:52 EDT
Article-I.D.: ucbvax.20271
Posted: Mon Aug 24 12:43:52 1987
Date-Received: Tue, 25-Aug-87 03:45:30 EDT
References: <120@snark.UUCP> <86@thirdi.UUCP> <8707@ut-sally.UUCP>
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: kube@cogsci.berkeley.edu.UUCP (Paul Kube)
Organization: University of California, Berkeley
Lines: 46
Keywords: simplicity elegance beauty truth ockham's razor

In article <100@thirdi.UUCP> sarge@thirdi.UUCP (Sarge Gerbode) writes:
>In article <20194@ucbvax.BERKELEY.EDU> kube@cogsci.berkeley.edu.UUCP (Paul Kube) writes:
>
>>But a theory may make more assumptions
>>(even logically stronger ones) than another, and yet have each of its
>>assumptions play an explanatory role.  Ockham's razor enjoins us to
>>disbelieve the first theory, other things being equal; and I'm still
>>wondering if there's an argument for it.
>>
>
>I think if one theory has greater explanatory power than another, the two
>theories don't satisfy the conditions for applying Occam's Razor...

That's why I said "other things being equal".  	I was supposing that
the only difference between the two theories was their "size" given
some metric on theories.  Others have suggested the metric be the
number of assumptions that the theory makes; I don't like this much
since assumptions seem hard to count but I'll go along with it for
sake of argument.  It's also unclear how to order theories with
respect to "explanatory power"... I've been assuming two theories to
have the same explanatory power if they license all the same
inferences among observation sentences, but this hasn't played much of
a role in the discussion yet.  (So if one of two equiexplanatory
theories has a logically stronger assumption set than the other, it
means the nonobservaton sentences it entails are a superset of the
other; they entail the same observation sentences.)

>(How do you spell that, anyhow?). 

My Webster's prefers Ockham, giving Occam as a variant.

>The law (as I understand it -- I hope the same way
>Occam did) states that of two explanations, each of which fits all the
>available facts equally well, one should pick the simpler or more modest
>one.  

Yes, "Don't multiply entities beyond necessity" is the gist of it.  And
there are reasons for taking this advice:  You tend to get theories
that are easier to understand, and maybe easier to use in practice
(though simplifying one's ontology can make a theory harder to use;
cf.  Hartry Field's _Science without Numbers_).  But some people
(maybe Ockham himself) wanted to say that one should always pick the
simpler theory *because it's more likely to be true*, and I have
been wondering what reasons there are for believing *that*.

--Paul kube@berkeley.edu, ...!ucbvax!kube