Predicate noun phrases (NPs) have different patterns of case in different languages. Even closely related languages can show significant differences (Sigurðsson 2008). For example, among the Germanic languages, Danish, Norwegian and English standardly assign accusative case to predicate NPs, while Icelandic, Swedish and German have nominative predicate NPs (Maling & Sprouse 1995: 168).
Modern English regularly uses the accusative/objective case for predicate NPs (with a few possible exceptions in learned constructions, such as the acceptability for many speakers of sentences like "It is he who is..."—probably generated by a "him who" > "he who" "virus", considering the common overextension to contexts like "Let he who is..."—and the unacceptability for many speakers of sentences like "*That is whom he is"—but whom behaves differently from normal accusative NPs in other ways also, and "who" is the usual pronoun used in accuative contexts).
However, I don't think it is theoretically impossible for a version of English with nominative predicate NPs to exist, or to have existed. (If there are actually good theoretical reasons to suppose this is impossible, I would appreciate learning about them!)
I asked a question on ELU a while back about the prescriptive "traditions" about what case to use for predicate NPs in English in various contexts after non-finite forms of "to be" when nominative NPs are treated as a potentially grammatical option. There doesn't seem to have been any clear consensus.
But I ran into an annoying situation: some of the grammatical explanations of the rules I encountered in old prescriptive grammar books seemed very unconvincing, but I couldn't see any way of refuting their conclusions aside from the simple empirical counterargument "nobody speaks that way," which is true but not very deep or interesting. Even if the rules seem arbitrary and senseless to me, for all I know it could be possible for a language to work that way. That bothers me a bit, because the rules don't just feel inconsistent with reality to me; they also seem to be in some way internally inconsistent, and I was hoping I would be able to support this feeling somehow.
So, I tried to look up some contemporary literature about case assignment to see if we have learned anything since the era of the prescriptivist writers that either adds support or takes support away from their prescribed rules.
But after reading a bit, I still feel just as ill-equipped to evaluate the patterns of case usage described in e.g. Reed and Kellogg (who prescribe "Its being he should make no difference" alongside "I wish to be him".)
Icelandic has complicated patterns of case usage that are apparently challenging to describe in terms of modern case theory (Sigurðsson 2008). German speakers use predicate nominative NPs in contexts where it doesn't seem theoretically possible for nominative case to be assigned structurally (Haider 2010: 264 (6.3.2)), posing a problem for Maling & Sprouse's hypothesis that predicate NPs in Germanic languages always receive case structurally through specifier-head agreement (1995). It seems like just about anything goes.
In fact, Sigurðsson (2008) actually argues (to my understanding) that there is a fundamentally non-one-to-one relationship between morphological case and the thing that syntactic theories of "Case" are about. If true, this would seem to sharply limit our ability to predict the distribution of morphological cases in a language using information about other morphological and syntactic patterns of the language (Sigurðsson references a quote from Jespersen 'no one ever dreamed of a universal morphology'). (While I was writing this question, I was shown a link to the question Are there any recent articles on the current state of Case theory? that mentions Marantz (1991), who also seems to take the position that m-case is not particularly correlated to the abstract "Case" of generative grammar.)
Reading Sigurðsson's arguments made me pessimistic, but I'm still curious:
Does anyone know of literature that analyzes how a version of English with nominative PCs might or did "work" according to some modern theory of morphological case, and that gives predictions about which morphological case(s) would be grammatical after non-finite forms in various contexts (e.g. to-infinitives after various types of subject control verbs and object control verbs, to-infinitives used as the subject of a clause, gerunds with genitive subjects)?
Is anyone familar enough with contemporary theories of (m-)case to be able to do such an analysis, and describe it to me in an answer?
- Haider, Hubert. 2010. The Syntax of German.
- Maling, Joan and Rex A. Sprouse. 1995. Strutural Case, Specifier-Head Relations, and the Case of Predicate NPs.
- Sigurðsson, Halldór Ármann. 2008. Externalization: the case of C/case. Lund University