Principled Comparative Method - a new tool

[Sean Crist]

On Tue, 24 Aug 1999, Robert Whiting wrote:

> And it is incorrect to describe "In the best case it [a reconstruction]
> is only the statistically most probable original relationship between
> the forms found in the daughter languages" as a statement about the
> comparative method.  Please read what is said before going into
> knee-jerk reactions.  Nothing was said about the comparative method.

All right.

If I'm recalling correctly, the author of the original message said that
one of the things he was measuring was the "distance" between attested
forms and reconstructed forms.  Since the Comparative Method is the only
widely accepted method for reconstructing prehistoric forms, I assumed
that the writer was going with reconstructed forms produced by the
Comparative Method.  You're right, tho, that he didn't specify that this
is the case.

> The comparative method doesn't compute anything.

It does.  It's essentially a function which takes attested languages as
its input and gives reconstructed languages as its output.  In principle,
a program could be written to do it; the major unsolved problem is
modeling the semantics in a way that allows a program to make human-like
judgments regarding what semantic developments are reasonable.  The
phonology, tho, could almost certainly already be computed by program.

> Although the comparative method is one of the major tools of
> historical linguistics it is not the only one and it does not
> give a "best case" reconstruction.  In general, it doesn't give
> you a reconstruction at all.  What it gives you is the idea that
> there is something that two different but similar forms that do not
> contrast could have both developed from.  It doesn't tell you what
> that something is.  If you have /b/ and /f/ in complementary
> distribution in two languages (or even in the same language) you
> can use the comparative method to show that they might be descended
> from the same phoneme.  You can call that phoneme */b/ or */f/ or
> *[labial consonanat], but the only thing that you can tell about it
> phonologically is that there should be some reasonable path from it
> to both /b/ and /f/.

Yes, I've made essentially this same point on this list before: the
Comparative method reconstructs phonological categories, not the
prehistoric phonetic realizations of those categories.  I phrased it in
different terms, but it's essentially the same point.  The Comparative
method _does_ give a reconstruction; just not one of the phonetics.

> But don't automatically associate "reconstruction" with "comparative
> method" in your mind.  And keep in mind that the discussion was about
> reconstructions in Middle Chinese which is an attested language so
> there may very well be statistical means of arriving at the best
> reconstruction.

If there's some other way of going from attested forms to reconstructions
of prehistoric forms without using the Comparative Method, I'd like to
know about it.  The only reason we're able to say anything at all about
prehistoric languages is that sound changes have a particular property,
namely, they are exceptionless (with a small amount of hand-waving here).
The Comparative Method crucially exploits this property of sound changes.

> You seem to be confused about what the topic of discussion is.
> Basically it is about measuring pathways of change between two
> daughter languages and a parent to see which of the daughters
> is closer to the parent *when all three are known*.  The method
> was described in a message posted by Jon Patrick on Thu, 12 Aug
> 1999 (see http://listserv.linguistlist.org/cgi-bin/
> wa?A2=ind9908&L=indo-european&O=T&P=11528 for the message; note put this
> URL back together before using it).  Essentially the method is like
> counting up the little numbers between the stars on your Texaco road
> map to figure which route between two places is the shortest.

I understand the idea of computing an optimal path perfectly well, and
I've understood from the start of the thread that this was the methodology
being employed.  My question is this: exactly what happens during the
transitions in the probabilistic automata, and how are the probabilities
for the transitions determined?

Automata normally perform a concatenation operation across each arc
between states.  One can imagine an automaton-like machine where the
transitions can perform other sorts of operations, such as an umlaut rule
(i.e., context sensitive substitutions). I'm not sure whether it's proper
to use the term "automaton" to describe this richer sort of machine.  But
if the machine in question is strictly concatentative (as automata at
least canonically are), I'm puzzled as to how you would model historical
sound change in such a machine, since historical sound change isn't
concatenative.

>> Not as bad as you think, because you can often tell from the relative
>> chronology that the change must have happened independently.

> Which is why it is easier to do historical linguistics with languages
> that have a history.  But if you only have, say, the modern forms, as
> in many African or Polynesian languages, it is almost impossible to
> tell common retention from independent innovation from influence of
> one of the daughters on the other.

That's not true at all.  Whether or not loans happened in the light of
written history, you can identify a word as a loan from a related language
because of the sound changes it has and has not undergone.  For example,
while English "cardiac" does ultimately go back to the PIE word for
"heart", you can readily tell that it is a loan from a non-Germanic
language, because it has not undergone Grimm's Law, which applied
exceptionlessly in prehistoric Germanic.  This same method of identifying
loans among related languages works just as well for languages which don't
have a long written tradition.

Now, it's true that there is a problematic case: it's hard to detect loans
which occurred between related languages soon after their branching,
before very many of the telltale sound changes took place.  This appears
to have happened between Germanic and Italo-Celtic, but it's very hard to
tell that it did happen using traditional methodology.  However, there are
many many cases where you can identify the loan words as I described.

You don't need a long written tradition to be able to work out the
relative chronology of prehistoric sound changes.

  \/ __ __    _\_     --Sean Crist  (kurisuto at unagi.cis.upenn.edu)
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