Circularity & testing.

Tom DiBenedetto tdib at UMICH.EDU
Sat Oct 19 13:35:04 CDT 1996

On Sat, 19 Oct 1996 12:21:23 -0700, James Lyons-Weiler wrote:

>The shift of the focus towards homology really misses the point of whether
>reciprocal illumination is circular or not.

Whether reciprocal illumination is circular or not, it is ubiquitous
in science. No, I dont think it is circular.

>Hypotheses can't be used to test hypotheses.

Hypotheses are combined parsimoniously under the expectation that
they will be congruent if they are true (and yes the fact that they
may be congruent doesnt PROVE they are true). They are tested against
an expectation deduced from basic evolutionary principles.

> 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?

>Cladistic parsimony alone cannot test anything, except for the hypothesis
>that tree T is indeed the shortest tree for a given data set.  Who would
>want to use an erroneous tree to test otherwise excellent hypotheses of

??? If the hypotheses are so excellent, then the tree is gonna be
equally excellent, for it is nothing but the combination of the
hypotheses, with a bit of fracturing done on those characters which
are incongruent with the preponderant pattern.
Tom DiBenedetto
Fish Division
Museum of Zoology
University of Michigan

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