# Fuzzy Class Theory

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**Fuzzy Class Theory** (or **FCT**) is a foundational theory for formal fuzzy mathematics introduced in the paper *Fuzzy class theory* by Libor Behounek and Petr Cintula. FCT can be characterized as (Henkin-style) higher-order fuzzy logic, or (Russell-style) simple fuzzy type theory. In the original article, it was defined over the logic LPi; nevertheless, it can be defined over any deductive fuzzy logic, e.g., MTL, BL, etc.

The theory has been proposed as a formal foundation of fuzzy mathematics. There is an ongoing project on developing fuzzy mathematics within the foundational framework of FCT.