 In addition to the degree of clarity it brings to the issues, a compelling reason for expressing the possibilism-actualism debate in formal terms is how starkly it illustrates the inextricable link between logic and metaphysics, in particular, the dramatic impact our metaphysical choices have on quantified modal logic. Arguably the best known illustration of this is seen in the validity of the inference from  (2)  to  (4)  in SQML and, more generally, in the validity of the Barcan  Formula:[43]