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Logic and rhetoric
Fuzzy logic is a class of logics in which a finite set of discrete truth values (e.g., "true" and "false" in binary logics) is replaced with an uncountable continuum of truth values, generally the set of real numbers between 0 and 1.
Fuzzy logic is related to probabilistic logic, in which truth values convey a probability that a sentence is true in the same sense as binary logic; e.g., if the truth value of proposition A is 0.5, it means that A has a 50-50 probability of being true, but still must be either wholly true or wholly false. In fuzzy logic, by contrast, a truth value of 0.5 means that a statement is only "half true;" for example, if a proposition "The glass is full" had a truth value of 0.5, it could be interpreted as "The glass is half full."