This is a preview. Log in through your library . Abstract We investigate, for several modal logics but concentrating on KT, KD45, S4 and S5, the set of formulas B for which ̅B is provably equivalent ...

This is a preview. Log in through your library . Journal Information The Journal of Symbolic Logic (JSL) was founded in 1936 and it has become the leading research journal in the field. It is issued ...