Re: The differences between traditional and phylogenetic taxonomicthought, an...

[Philidor11@aol.com]

In a message dated 7/7/99 4:07:17 PM Eastern Daylight Time, 
znc14@TTACS.TTU.EDU writes:

<< Isn't any finding of fact subject to change no matter how well-informed it 
may currently be?  I believe in logic, but not in its ability to find the 
only correct answers with limited data and alternate reasonable 
possibilities.>>
 <True. However, as related above, monophyly by definition is a philosophical 
and logical question, not a testable hypothesis. You can question the logical 
process used to derive the result, but you cannot test the result directly (I 
think... anyone better at this stuff think otherwise?). >

I laid out your posting on paper to follow some fairly sinuous logic.
Just briefly, I laid out your five stages in the history of classification:
1. taxononomy is an artificial classification
.    described as hierarchical
2. taxonomic classification represents a divine plan
.    based on the Scala Natura, a hierarchical way of analyzing nature
.    I'm not sure that this stage is not just an analysis of the basis for 
stage 1                       
3. taxonomic classification [presumably unchanged] represents phylogeny
.    propinquity of descent, families giving rise to other families
4. phylogenetic hypothesis gives the taxonomic classification
.   'Monophyletic taxa were demanded, with the result that taxa were finally 
real         .    evolutionary units (clades). Taxa were still errected in a 
traditional manner,           .    however, with the result that they were 
not necessarily clades by definition.'
.    Taxa were clades, but were not clades by definition.  Hmmm.  I think 
this means  .    that the way taxa were spoken of still relied on characters, 
but the preferred         .    definition would not refer to characters.
5. phylogeny is represented by taxonomy
.    taxon names are assigned to clades identified by their 
ancestor-descendant         .    relationships, eliminating the last vestiges 
of character- or content-based             .    taxonomy.  Stage 5 is no 
longer a classification system.
In fact, when we reach stage 5 'monophyly by definition is a philosophical 
and logical question, not a testable hypothesis'.  The entire exercize 
replacing 'classification' is based on positing a clade ('they [clades] are 
out there') and then trying to fill it (how?).  I'm not sure what the product 
of stage 5 might be, except possibly a single all-inclusive clade if life 
appeared once, but you have defined it as a closed system.  (That's the type 
which can never be tested and so can never be refuted.)
Going back to stage 4, which at least is definitely paying attention to the 
animals' characters and whose groups might be refuted, presumably, you 
observe:
<<Think about it liek Heisenberg's Uncertainty Principle: we can (a) know a 
group [discerned how?] is monophyletic and test which taxa the group 
includes, or we can (b) take a group of taxa and test if it is monophyletic. 
You can't do both, and different methods approach the problem differently.>> 
Your (b) logic appears to refer to stage 4.  You said 'Dr. Brochu was using 
Stage 5
methodology, but writing in terms of Stage 3 to relate to that audience.'   
However, because hypothesis testing to see if a group exists is 
characteristic of stage 4, I think you mean a stage 4 methodology.  Unless he 
begain with the concept that a group existed, defined before the group is 
known to include any animals (else a hypotheis that animals were related 
would have been tested in the past), and then tested to see if anything could 
be included.  I never thought that approach was possible... 
The difficulty with stage 4 was how you knew when you were right.  Getting 
facetious, the difficulty with stage 5 is knowing what you're right about.  
In the absence of a proven ancestor, identifying descendants still seems to 
return to similarities among animals.  And identifying which similar 
characters are important among a specific set of animals still seems an 
exercize in judgement.
How'm I doing?