Family resemblance concepts contain no necessary conditions, only sufficient resemblance.

Evidence

However, developments in philosophy, logic, and cognitive psychology have shown that there are other ways to construct concepts. I shall focus on the “family resem­ blance” concept structure which is in many ways the polar opposite of the necessary and sufficient condition one. In their groundbreak­ ing article Collier and Mahon (1993) introduced the idea of family resemblance concepts into the political science literature. The family resemblance structure can be seen as the opposite of the necessary and sufficient condition one because it contains no necessary con­ ditions. All one needs is enough resemblance on secondary-level di­ mensions to be part of the family. — Gary Goertz, Social Science Concepts, 46

Categorization

• DEFINE: Defines family resemblance structure and contrasts it sharply with necessary-and-sufficient concepts.
• XREF: Connects to Wittgenstein’s family resemblance idea and to Collier and Mahon’s introduction of it into political science.