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Re: Kileskus and Proceratosauridae
A tautology is a statement that is always true.
"It was a fast speedster" is not always true.
"If I am wrong, then I am not right" Is always true, and thus is always true.
"We'll get there when we get there", or "When I'm right, I'm right", are always
true, and thus are tautologies.
"Reptiles are a monophyletic clade" is not always true depending on how you
define reptiles (such as when it excluded birds and included many synapsids).
However, if a clade is monophyletic by definition, then the statement "The
clade is monophyletic" is always true, and thus a tautology (assuming "the
clade" exists at all)
Monophyletic clade is just redundant, it takes more to turn it into a tautology.
--- On Wed, 3/31/10, Raptorial Talon <email@example.com> wrote:
> From: Raptorial Talon <firstname.lastname@example.org>
> Subject: Re: Kileskus and Proceratosauridae
> To: DINOSAUR@usc.edu
> Cc: "DML" <email@example.com>
> Date: Wednesday, March 31, 2010, 1:37 AM
> "It is true, in fact, that
> "monophyletic clade" may be a tautology,"
> Not picking on any one person here, but a semantic
> nonetheless: How can "monophyletic clade" be construed as a
> It's merely redundant. A phrase like "big giant" or "fast
> is not, itself, tautological; it just repeats the same
> concept with
> different wording.
> AFAIK, a true tautology is a form of argumentation in which
> unsubstantiated points are cited as mutual evidence, each
> proving the other, but neither being critically examined.
> The classic
> example I was taught was, to paraphrase, "for a long time,
> would argue that dinosaurs had to have been cold-blooded,
> because they
> were reptiles, but then they would turn around and argue
> dinosaurs must have been reptiles, because they were
> The veracity of the example aside, it does illustrate a
> tautology (IIRC): neither argument has been demonstrated
> satisfaction by independent observations, yet each is cited
ence when the other is questioned. It's a loop
> where the argument
> goes in circles, an untested claim being cited as proof for
> untested claim - and then vice-versa when challenged.
> As for my opinion of paraphyletic "clades," I do have to
> object to
> that terminology. There's already a perfectly legitimate
> term for
> that: grades. Since grades =/= clades, and since "grade" by
> definition refers to a paraphyletic assemblage of taxa,
> using "clades"
> in such a context is extraneous at best. It's pointless as