Semanticists often restrict their theories by imposing constraints on the parameters that can be employed for interpreting the expressions of a language. Such constraints are based on non-logical features of actual contexts of utterance, but they often have important effects on issues that do pertain to logic, like analyticity or entailment. For example, Kaplan’s restriction to so-called “proper contexts” was required in order to count “I am here now” as valid. In this paper I argue that constraints of this kind (...) are often posited in an arbitrary and non-consistent way, and that they yield the intended results only at the price of imposing ad hoc principles whose justification could in turn justify further, often undesirable restrictions into the theory. I also introduce a criterion for telling whether such constraints are imposed in a legitimate manner. (shrink)