Mutual-exclusivity rules erase real cases that belong to two adjacent categories

Evidence

Typologies multiply the dichotomization problem because normally multiple dichotomizations are performed. Another way to view the mutually exclusive rule is that it denies the existence—and implicitly the importance—of the empirical fact that an observation belongs to two semantically near concepts. The overlap is that semantic area that the two types have in common. — Gary Goertz, Social Science Concepts and Measurement, 1230

Categorization

• DEFINE: Defines ‘overlap’ as the shared semantic area of two types — the thing exclusivity rules pretend does not exist.
• DEEPTHINKING: Recasts a supposedly technical rule as an empirical denial: every typology silently asserts that overlap cases don’t matter.