Jon,
There are several points that must be considered. The first is that all modern
versions of modal logic after C. I. Lewis (including those based on post-1970
methods) are consistent with or variations of one or more of the versions
specified by Lewis). That includes the versions of modal
List:
As I continue contemplating my updated candidate for Delta EGs (see earlier
posts below), I am finding that, in conjunction with the laws and facts
semantics (LFS) developed by Dunn and Goble, it is very helpful for
explicating the effects of adding various modal axioms to classical logic.
