Human sciences require fuzzy logic because concepts have unsharp boundaries

Evidence

Bivalent logic is not the right logic for serving as a foundation for human sciences. What is needed for this purpose is fuzzy logic. Essentially, fuzzy logic is the logic of classes [concepts] with unsharp boundaries. — Gary Goertz, Social Science Concepts and Measurement, 567

Categorization

• DEFINE: Defines fuzzy logic as the logic of classes with unsharp boundaries, set against bivalent classical logic.
• XREF: Connects to the book’s earlier degreeism and family resemblance machinery, now reconstructed on a fuzzy-logic foundation.