3TA

[René Zaragüeta i Bagils]

Dear Dr. Colless,

if you are refering to me as the one discussant, this is what I think :

Characters = classificatory concepts that partition (hierarchically) a
population on instances and non-instances of the character. Charatcer =
homology = synapomorphy.
Multi-state character: a character comopsed of paralog characters (that is,
a concept composed of concepts).
Taxon: an ensemble of characters (because cladistic analysis is analysis,
and parts are characters).

All these definitions are not mine (most are from Nelson, 1994, Homology and
systematics in the book edited by Hall ; others come from Lebbe, 1991, etc.)

When you say "character" = "part", it seems you think of a part as being
"real", in an atomistic sense. When I wrote "part" I meant description of a
part of an organism, that is, a sub-concept of a more inclusive concept.
Do you mean that from your viewpoint characters and taxa are real, in an
essentiallistic sense? This gives sense to your citation of Russell. I have
never talked of taxa as objects, and I have rarely heard about such a
conception. But to conceive a hierarchy of concepts has nothing to do with
this. (Russell could hardly deny that there are hierarchies of concepts in
Mathematics, I guess).
I guess that you don't agree with the common idea of characters as theories
(= concepts)?
I agree with the conception that characters = theories. Scales (a character,
a concept) is paraphyletic if it does not include feathers, as reptiles are
paraphyletic if they do not include birds.
Characters defining paraphyletic taxa are paraphyletic, I don't see why this
should be a problem, and why "paraphyletic" should be applied to more or
less inclusive concepts only.


René Zaragüeta Bagils
Département Histoire de la Terre UMR 8569
Equipe SICC (Systématique, Informatique, Cladistique et Chronologie)
Muséum national d'Histoire naturelle
8 rue Buffon
75005 Paris - France