00100	THOUGHTS ON WINOGRAD'S ABSTRACTIVE HIERARCHIES
00200			K.M. COLBY
00300	
00400		From experience with belief systems we have found  a  typical
00500	sort  of  confusion  can  develop  in  constructing  hierarchies  (or
00600	lowerachies). First let  us  distinguish  between  the  singular  (or
00700	specific) and the general and between concrete and abstract.
00800		Concrete general terms  are  often  misinterpreted  as  class
00900	names  and  thus  become treated  as abstract singular terms. This is
01000	likely when a general term is expressed in a  grammatical  plural  as
01100	in:
01200			Cats are furry.
01300	To a logician this expression means that anything that is  a  cat  is
01400	furry.  Both  "cats"  and  "furry" are concrete general terms. Plural
01500	nouns  are  not  class  names  unless  abstract  general  terms   are
01600	predicated on them.
01700		There are two dimensions here which  must  be  distinguished:
01800	(1) concrete-abstract and (2) specific-general. A hierarchy along the
01900	concrete-abstract dimension would be:
02000			Fido → Dog → Species
02100	in which the singular terms refer respectively to an object, a class,
02200	and a class of classes. Predicates on classes of classes are rare  in
02300	nontechinical    natural   language.   This   dimension   should   be
02400	distinguished from the specific-general of:
02500			Fords → Cars → Vehicles
02600	in which the terms are at the same level of abstraction but differ in
02700	generality.
02800		These  distinctions  are  important for a simple reason : the
02900	generality relations are transitive  whereas  the  relations  between
03000	levels  of abstraction are intransitive. In traversing a memory graph
03100	(making sure that the path does not involve changes in senses of  the
03200	tokens (otherwise horrible loops)), you don't want to conclude that:
03400			Fido isa species.
03500		One reason Piaget's questions to  children  received  strange
03600	answers  was  that he repeatedly mixed up these two dimensions in his
03700	linguistic expressions. If you are careful about how you  phrase  the
03800	question,  it  is clear that a child does not really believe that one
03900	has more CANDY after a candy bar is broken into pieces.