T-norm-based fuzzy logics and logics for reasoning under vagueness

We contrast the concept underlying t-norm-based propositional fuzzy logics with the problem to whose solution fuzzy logics are frequently suggested as helpful – namely, to find a model of reasoning with vague information. We argue that fuzzy logics are useful as long as truth values can be identified with the meaning of the considered propositions. This, however, is rarely the case in practice; hence we see the need to broaden the concept underlying this important class of logics and try fresh approaches. In particular, we should flexibilise the formalism to allow that propositions do not arise in the same context, but are just known to be related in some