Use a systematic test. First check both-way inclusion (equality); then absence of overlap (disjointness); then one-way inclusion (absolute inclusion); finally overlap with members exclusive to each (partial overlap). A correct classification rests on the exact range of both concepts.
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A four-question diagnostic
Four Relations Between Universal Concepts
Use a systematic test. First check both-way inclusion (equality); then absence of overlap (disjointness); then one-way inclusion (absolute inclusion); finally overlap with members exclusive to each (partial overlap). A correct classification rests on the exact range of both concepts.