Fuzzy Logic

• is a form of many-valued logic in which the truth values of variables may be any real number between 0 and 1 both inclusive. It is employed to handle the concept of partial truth, where the truth value may range between completely true and completely false. By contrast, in Boolean Logic/First-Order Logic, the truth values of variables may only be the integer values 0 or 1
• an extension of the case of multi-valued logic, valuations (𝑢:𝑉_𝑜→𝑊) (𝑉_𝑜 - propositional variables & 𝑊 - set of membership degrees) can be thought of as membership functions mapping predicates into fuzzy sets (or more formally, into an ordered set of fuzzy pairs, called a fuzzy relation). With these valuations, many-valued logic can be extended to allow for fuzzy premises from which graded conclusions may be drawn

Fuzzy Logic - Probability?

see: Logic