 The interpretation of continuum-valued logics in terms of fuzzy set theory has for some time be seen as defining the field of mathematical fuzzy logic. Susan Haack (1996) refers to such systems of mathematical fuzzy logic as “base logics” of fuzzy logic and reserves the term ‘fuzzy logics’ for systems in which the truth values themselves are fuzzy sets. Fuzzy logic in Zadeh’s latter sense has been thoroughly criticized from a philosophical point of view by Haack (1996) for its “methodological extravagances” and its linguistic incorrectness. Haack emphasizes that her criticisms of fuzzy logic do not apply to the base logics. Moreover, it should be pointed out that mathematical fuzzy logics are nowadays studied not in the first place as continuum-valued logics, but as many-valued logics related to residuated lattices (see Hajek 1998; Cignoli et al. 2000; Gottwald 2001; Galatos et al. 2007), whereas fuzzy logic in the broad sense is to a large extent concerned with certain engineering methods.