 However, these results apply to basic modal logic; in that logic we are talking about satisfiability as meaning “satisfiable on some model”, no restrictions (like transitivity) are imposed on the accessibility relation. And for any modal logic other than system K we are looking for models with additional properties. It is true that similar method can be applied with other propositional systems when the relevant properties can be expressed by first-order formulas with only two variables. Nevertheless, transitivity is a clear counter case.