Circularity & testing.

Tom DiBenedetto tdib at UMICH.EDU
Sat Oct 19 14:47:43 CDT 1996


On Sat, 19 Oct 1996 13:57:35 -0700 (PDT), James Lyons-Weiler wrote:

>On Sat, 19 Oct 1996, Tom DiBenedetto wrote:
>It is not ubiquitous in science.  Just because a pattern is sensible does
>not mean that the sensing of the patter constitutes a test of how sensible
>that pattern is.  See how ridiculous it is?

Yup. Your sentence is *perfectly* ridiculous, both in a logical
sense, and as a charracterization of cladistics.

>I never expect any test to PROVE anything.  My point was that trees, as
>hypotheses, can't test hyotheses of homology.  The trees are derived from
>the hypotheses of homology, and then are supposed to provide a test of
>homology?  Posh.

One more time....the tree itself is not turned back to test the
hypotheses, the test is a test of congruence; the tree is the result.
What is so difficult about this?
Do you know what a hypothesis of homology is?

>> > > Even when the assessment of homology is good, the
>> >tree that has the most among character agreement can be erroneous (this we
>> >know from simulation and known phylogenies).
>>
>> Everyone has always known that; what do you think this is an argument
>> for or against?
>I think it's an argument against using trees to test hypotheses of
>homology.

I think you wrong.

>No, when homology is dead on, the trees can be dead wrong.  Where is the
>test?

HUH? That is absurd.
---------------------------------------------
Tom DiBenedetto
Fish Division
Museum of Zoology
University of Michigan




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