In the mood for S4: the expressive power of the subjunctive modal language in weak background logics (Q2352453)

The expressive equivalence of subjunctive modal language (SML) (see [\textit{K. F. Wehmeier}, ``Subjunctivity and conditionals'', J. Philos. 110, No. 3, 117--142 (2013; \url{doi:10.5840/jphil2013110335})]) and the actuality modal language (AML), a modal language enriched by an actuality operator forcing formulas within its scope to be evaluated at the actual world, was shown by Wehmeier [loc. cit.], when the background modal logic is quantified \(\mathbf{S5}\). In this paper, the author shows that AML is strictly expressively stronger than SML, when the background modal logic is weaker than quantified \(\mathbf{S5}\).