Message from discussion Sean Pitman and nested hierarchy
From: John Harshman <jharshman.diespam...@pacbell.net>
Subject: Re: Sean Pitman and nested hierarchy
Date: Thu, 28 Feb 2008 16:34:27 GMT
Organization: SBC http://yahoo.sbc.com
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Perplexed in Peoria wrote:
> "John Harshman" <jharshman.diespam...@pacbell.net> wrote in message news:jXkxj.firstname.lastname@example.org...
>> Perplexed in Peoria wrote:
>>> "John Harshman" <jharshman.diespam...@pacbell.net> wrote in message news:r94xj.4949$Mh2.email@example.com...
>>>> Perplexed in Peoria wrote:
>>>>> "John Harshman" <jharshman.diespam...@pacbell.net> wrote
>>>>> (quoting Pitman):
>>>>>>> As far as I've been able to tell, your argument is basically that a
>>>>>>> nested hierarchical pattern implies common descent in all cases where
>>>>>>> it is found. This hypothesis does seem to hold true, as far as I can
>>>>>>> tell, for non-deliberate processes. It seems that non-deliberate
>>>>>>> processes cannot make a nested hierarchical pattern without the use of
>>>>>>> common descent. In fact, this particular hypothesis, is actually
>>>>>>> falsifiable. All one has to do to falsify this hypothesis is show a
>>>>>>> non-deliberate process producing a nested pattern without using common
>>>>>>> descent and this hypothesis would be falsified.
>>>>> Ok. I'll bite. Is alphabetical order a kind of nested heirarchy? Seems
>>>>> to me that it is. Words beginning with the same letter are in the same
>>>>> phylum. Words beginning with the same pair of letters are in the
>>>>> same order. Etc.
>>>>> Now, if you accept that this is a nested heirarchy, then please notice
>>>>> that the heirarchy itself is in the mind of the systematizer, rather than
>>>>> in the process which generates the words - whether deliberate or not.
>>>> So what you have there is a deliberate process imposing a nested
>>>> hierarchy on data that aren't inherently hierarchical. What was your
>>>> purpose in doing that? It doesn't seem to be arguing either for or
>>>> against anything Sean said.
>>> My purpose here is simply to explore how strongly the observation
>>> of a nested heirarchy suggests the hypothesis of common descent.
>>> I accept the point made by several people that my alphabetical-order
>>> example was flawed mostly because the heirarchy gets built based
>>> on a single criterion. Whereas the biological nested heirarchy used
>>> as evidence for common descent has the property that the tree is
>>> 'robust' in that you get pretty much the same tree whatever criterion
>>> you choose at each stage. That 'robustness' is what gives the tree
>>> its predictive power.
>>> So the question I want to look at this time is whether the existence
>>> of this kind of robust classification heirarchy is necessarily evidence
>>> for common descent.
>>> Let us consider the classification of books in a bookstore by genre.
>>> Phylum 'fiction'. Order 'F&SF'. Family 'Sword and Sorcery'. Is
>>> the Heirarchy 'natural'? I think so.
>> I think not. Genre is moderately arbitrary, and classifying the books by
>> genre is itself arbitrary. Why not by author, or subject, or color?
> <Smile> I took this objection seriously enough to think long and hard
> about what feature of the biological nested heirarchy protects it from the
> charge that it too is 'arbitrary'. And the answer I came up with is that
> in the case of biology there is a 'true tree' - however difficult it may be
> to discern the true tree given the evidence available.
> But this observation is a bit useless (and circular) in the never-ending
> struggle against Pitman. </smile>
It's more useless than you imagine. Pitman agrees that there is a nested
hierarchy of life, and that it's non-arbitrary. So you are not arguing
with Pitman at all here. You're arguing with me about something we both
(Pitman and I, that is) agree on.
And the answer *I* come of with is that in the case of biology the data
really are hierarchal, and that this hierarchy is discovered rather than
imposed, and that it can be approached from many directions with the
same result. Now it's true that some aspects of the tree are easier to
find and agree upon than others. So? There are enough easy problems for
our purposes, including the all-important (to creationists) question of
>>> Is it predictive? I can probably
>>> make a pretty good guess as to whether a book belongs in this
>>> category just by looking at the cover art.
>>> Now, is this heirachy the result of common descent or intelligent
>> It's the result of imposing a hierarchy on non-hierarchical data (the
>> books themselves), same as the alphabetical order example.
> And the same as the biology example. The hierarchy is ALWAYS
> imposed - but one hopes it is imposed using 'natural' criteria. And
> that the hierarchy may be able to tell us something about the original
> source of our data. My impression is that this genre classification
> of books suggests the hypothesis that authors frequently write with
> a particular genre in mind.
All very nice. But the hierarchy of life is *not* imposed. It's inherent
in the data.
>>> To be honest, I'm coming to the opinion that an OEC
>>> doesn't really need to be an omphalist in order to have no fear
>>> of the nested heirarchy evidence, per se.
>> You will have to explain more clearly why this is.
> I hope I have made it a little clearer.
A little. Not enough, though. And not to the extent that I find your
>>> Of course, the actual
>>> sequence data provides too many examples of non-adaptive
>>> features that also fit the heirarchy.
>> Why should that matter? And why do you emphasize "non-adaptive"?
> Because people who like the ID hypothesis have a perfectly
> adequate explanation for why adaptive features might prove to fit
> naturally into a hierarchy. But they are stuck with omphalism as the
> non-common-descent explanation for the natural fit of non-adaptive
> features into a hierarchy.
What is that perfectly adequate explanation?
>>> Those do indeed tend to argue
>>> against ID. But I think we need another name for these bits
>>> of evidence - another name beyond Nested Heirarchy.
>> I'm still at a loss to determine why you think so.
> I hope you are a bit less lost now. ;-)
We're making some progress.