From relative proadverb to declarative complementizer: the evolution of the Hungarian hogy ʻthatʼ

The declarative complementizer has been claimed to have grammaticalized from a relative pronoun in various Indo-European languages. The source construction is assumed to have been the correlative sentence The initial phase of the hypothesized process, however, has remained unclear; in the explicative clause to which e.g. the Germanic -type complementizers can be traced back is already a complementizer base-generated in C rather than a relative pronoun in Spec,CP. This paper analyzes a similar developmental path, that of ‘that’, the Hungarian general complementizer cognate with the relative proadverb ‘how’, the early stages of which can be reconstructed more completely. It traces back to a canonical correlative construction, and documents the subsequent stages of its evolution from a relative operator binding a variable in a correlative sentence, via a linker introducing an adjunct clause, to a complementizer subordinating a clausal argument to a matrix predicate.