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Thinking critically requires the ability to categorize. This ability is
basic (foundational) because proper language use depends on it. Your ability
to communicate, both to understand what others are saying and to express
what you are thinking, depends on categorization. Categorization is needed
for clear and useful definitions, which are
also basic to critical thinking. Finally, categorization is the basis for
an entire branch of logic which we will study here as the Square
of Opposition, Immediate Inference and
the Categorical Syllogism.
Ideas that represent categories or types of things
The individual things referred to by concepts.
A broad concept which includes narrower concepts that pick out subgroups
from all the referents in the genus.
A narrower concept included under some genus. A species picks out one type
of the larger class. Genus and Species are relative terms. For example
DOG is a species of MAMMAL, but DOG is a genus for POODLE.
A Basic Principle:
In a good categorization every item to be categorized will fit under some
category and no item will fit under more than one category. (Nothing will
be left out and there will be no overlap.)