Does possible world semantics turn all propositions into necessary ones?

A number of philosophical and semantic analyses make essential use of the concept of a possible world. Following tradition, we will refer to this family of analyses as “possible world semantics” (PWS). The present work argues that there is no interpretation of the term “world” that validates even a single one of the doctrines composing PWS. It is argued that, depending on what the word “world” is taken to mean, PWS entails either that all modal terms (words like “necessarily” and “possibly”) are infinitely ambiguous or that all true propositions are necessarily true. It is also argued that David Lewis’ PWS-based analysis of counterfactuals can succeed only relative to decidedly retrograde conceptions of space and time. Most importantly, it is shown that PWS is false even if it finds a way to neutralize the arguments just described. Given certain truisms about spatiotemporal existence, it is a substantive modal question whether the worlds needed to validate PWS are even possible. (As we will see, there is reason to believe that many of those worlds are in the same category as worlds that comprise light but not electromagnetic radiation.) The modal status of these worlds cannot be non-circularly resolved within a PWS-framework, and must be therefore resolved within some other modal framework, showing that PWS is parasitic on some more fundamental understanding of modality.