Donald Byrd, School of Informatics and School of Music, Indiana University
rev. late January 2007
• Classification (in the ordinary way) is dangerous to your understanding.
– Classification ordinarily means hierarchic classification
– Hierarchic means subdividing cleanly into categories; often subcategories. But...
– Almost everything in the real world is messy
– Absolute correlations between characteristics are rare
– Example: some mammals lay eggs; some are “naked”
– Example: is the piano a keyboard, a string, or a percussion instrument?
– Example: Ginger Baker says Cream was “not really a rock group”
• 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 A, C, D…”
– NB: most fundamental one may not be the one mentioned first
• Important special case: partitions (“flat” classifications, without subcategories)
– Example: “Is Bred still in love with Jan, or is he having an affair with Operetta?”
– Example: arguments against faster-than-light travel
• 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
• So should we abandon hierarchic classifications?
– Of course not: they're much too useful
– But be on your guard for misleading ones!