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Re: Cladistic taxonomy (was Dietary factors)





T. Mike Keesey wrote:

On Tue, 8 May 2001, philidor11 wrote: 

<snip>

> Archie is part of the _definition_ of  birds.

This is the second time I'm making this point today; Archie is NOT part of
the definition of "bird". "Bird" is a vernacular term that means whatever
the body of English speakers at large determine it to mean. Archie is part
of the definition of _Aves_, a formal taxon which is not necessarily the
same thing as "birds".


Hmmm...
(a) At the risk of sounding stupid: what's Archie?

(b) Is ordinary language really that different from scientific terminology? Doesn't 'Aves' also mean whatever the relevant community of scientists says it means? Sure, scientific terminology is codified, but so is ordinary language, in ordinary dictionaries. In the case of scientific terminology as in the case of ordinary language, there's often a tug of war b/w the conservative force of codification and (r)evolutionary pressures from speakers. Scientific terminology certainly changes. Consider the way 'mass' changed when Einsteinian physics replaced Newtonian physics. Or consider the terminology at issue between the cladists and...the regularists...non-cladists...whatever they're called...


"Avian". It's only one letter longer than "bird", and so, so much more
precise.

> Bas VanFraassen sez: you don't need clear boundaries to have a legitimate
> distinction; all you need is a clear case of the one kinda thing and a clear
> case of the other kinda thing.

This works for vernacular terms like "bird". Not a great idea in formal
nomenclature, IMHO.


van Fraassen, for what it's worth, is talking about technical terms, too. Terms with clear and precise necessary and sufficient conditions for their application might be more desireable for some scientific purposes (though not for all), but vF is just claiming that you don't absolutely have to have 'em in order to have a legitimate distinction. Which is good, if he's right, b/c clear and precise necessary and sufficient conditions for the application of terms turn out to be very hard to come by. Even something like 'has feathers' probably isn't very precise, as there are probably intermediate cases between hairs and feathers that we'd be hard-pressed to classify.

NOW I'm shutting up...

wmk



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