Classification: Logician General’s Warning

Donald Byrd, School of Informatics and School of Music, Indiana University

rev. late October 2010

 

•       Classification is dangerous to your understanding.

–      Classification ordinarily means hierarchic classification

–      That means partitioning = subdividing cleanly into categories (& often subcategories). But...

–      (1) Almost everything in the real world is messy; very little is well-defined

–       (2) Absolute correlations between characteristics are rare

–       Example: some mammals lay eggs

–       Example: is the piano a keyboard, a string, or a percussion instrument?

–       Example: Was the first real piano Cristofori's (ca. 1700), Broadwood's (ca. 1790), or another?

–       Example: Cream member Ginger Baker says Cream was “not really a rock group”!

–       Example: Should e-mail from Jean about teaching go in the "Jean" folder or the "Teaching" folder?

•         People often say “an X has characteristics A, B, C, D…”

•         They nearly always mean “an X has characteristic A [or B or C or…], and usually also B, C, D…”

–       NB: most fundamental one may not be the one mentioned first

•         Important special case: partitions (“flat” classifications, without subcategories)

–       Example: “Are charter schools havens for innovation, or are they undermining public schools?”

–       Example: A famous (ex)physicist says arguments against faster-than-light travel are based on supposed partitions that aren't really partitions

•         Messiness of the real world leads to:

–       People who know better claiming absolute correlations

–       Arguments among experts over which characteristic is most fundamental

–       “Is it this or that or that?” questions that don’t have an answer

–       Don changing his mind

•         But lack of classification is also dangerous to your understanding!

•         So should we abandon hierarchic (or all) classifications?

–       Of course not; they're much too useful

–       Besides, it's impossible to avoid them; they're built into our ways of thinking

–       Best policy is (1) be on guard for misleading classifications; (2) be aware of alternatives

–       Alternative worth considering: "extended" hierarchies (e.g., Directed Acyclic Graphs instead of trees)

•         See Hayakawa, S.I., & Hayakawa, Alan R. (1990). Language in Thought and Action, 5th ed.