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Re: The iguanodont paper



evelyn sobielski writes:
 > A nice way to explain the problem of nonmonophyletic taxa to
 > laypeople by reductio ad absurdum: consider a taxon
 > "Caerulommatanimalia" - "animals with blue eyes". Kudos to Stefan
 > Obenauer at Cologne Zoo for that one.

Sorry to be picky, but this is not a reductio ad absurdum.  That is a
proof in which you start by assuming to be true what you want to prove
is false, then show that a contradiction ensues.

(To pick a famous, and easy to follow example, suppose we want to
prove that there are an infinite number of prime numbers.  Then start
by assuming there are an finite number of them.  In that case, we can
multiply them all together to make a huge integer.  But if we subtract
one from that integer, then the result is not divisible by any of the
smaller primes that we multipled together, and is therefore itself
prime.  So our initial assumption must have been false.)

What we have in the Caerulommatanimalia case is more like a straw-man
argument: you extrapolate and exaggerate your opponent's position into
one which is clearly false, and deduce (incorrectly) that his original
position was also false.  Classic examples: "evolution says that we
developed from amoebas by pure chance, so it must be wrong (and
stupid)"; and "relgion says that everything was created by an old man
with a white beard, so it must be wrong (and stupid)".

 _/|_    ___________________________________________________________________
/o ) \/  Mike Taylor    <mike@indexdata.com>    http://www.miketaylor.org.uk
)_v__/\  "I love English: in what other language can you make things so
         obscure by explaining them?" -- Zenlizard.