Darwin-L Message Log 6:20 (February 1994)

Academic Discussion on the History and Theory of the Historical Sciences

This is one message from the Archives of Darwin-L (1993–1997), a professional discussion group on the history and theory of the historical sciences.

Note: Additional publications on evolution and the historical sciences by the Darwin-L list owner are available on SSRN.

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<6:20>From p_stevens@nocmsmgw.harvard.edu  Sat Feb  5 08:08:14 1994

Date: 5 Feb 1994 09:08:43 U
From: "p stevens" <p_stevens@nocmsmgw.harvard.edu>
Subject: quinarianism (and Smith)
To: darwin-l@ukanaix.cc.ukans.edu

Why quinarism?  Why five kingdoms?  Why not binarism? (well, there were two
kingdoms of life until recently.)  I think that the "answer" may lie in the
fact that there are five figures in the (U.S.A.) zip code, not more.  Nine
numbers in the zip code or twelve kingdoms would simply be too hard to
memorise.  The title of G. A. Miller's article in Psychol. Rev. 63: 81-97. 1956
says it all:  "The magical number seven, plus or minus two: some limits on our
capacity for processing information."  It is perhaps easier to remember things
in small groups, and then one remembers that things come in small groups with
the same number of things in them, and then this becomes evidence of some
underlying reality...  In the early 19thC naturalists were flirting with a
whole variety of number systems from two to seven, as far as I remember.

There is also a very interesting paper by E. W. Holman, "Statistical properties
of large published classifications," J. Classific. 9: 187-210. 1992 that show
such small numbers as being a recurring and pervasive feature of well-worked
out biological classifications.  Indeed, one of the authors (Bentham) of the
botanical classic of the 19thC, the -Genera plantarum-, by George Bentham & J.
D. Hooker, was specifically trying to interpolate ranks throughout the
classificatory hierarchy so that no group would include more than 3 to 6 (to
12) members at the next lowest hierarchical rank. And that is exactly what they
succeeeded in doing, chunking up plants in such a way that the classification
as a whole fuctioned as a good memory system.  One attempts to extract
biological (= evolutionary, phylogenetic) meaning from such classifications at
some peril.

I haven't look at "folk" classifications from this point of view, but my guess
is that there is going to be some sort of intersection of prototype theory as
invoked by Berlin in his recent "Principles of Ethnobiological Classification",
at least some of the variants of biological typological thought (perhaps
particularly Farber's "classification type concept"), and these number systems.
 However, it is going to be important to look at the informal groupings of such
systems as well as the formal groupings.

As to Adam Smith, the reference I have is to "Essays on Philosophical Subjects"
[edited by W. P. D. Wightman and J. C. Bryce], Clarendon Press, Oxford, 1980,
II[roman]:12 - It refers not to the pagination of the book, but to Smith's
writings included in it.

Peter Stevens.

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