This article traces the historical development of complement constructions with matrices containing be + NP with wonder as well as those containing be + tweo/doubt, and proposes an analysis of them at two levels of generality. At the meso-constructional level, all the forms of (it/that) + be + wundor are analysed as historical variants of a predicative matrix and those with (of that) + (it/there) + be + tweo as historical variants of an existential clause. At the macro-constructional level, we argue that the two meso-constructions share the same schematic functional and structural components, which is evidenced by the fact that they both allow for comparable lexical and grammatical readings, and that the latter readings have the same paradigmatic variants, viz. parentheticals and discursively juxtaposed independent sentences. In view of this we posit a single macro-construction, with matrix and complement clause as the primary structural units. We thus propose a different analysis for the subtype with predicative matrix than the traditional it-extraposition account, which treats the that-clause as the extraposed subject of the whole construction, and views subject extraposition as a phenomenon sui generis. Against this, our analysis “respects the overt form” (Langacker 1991: 69) which the existential and predicative matrices and their complement clause have had through their whole history, and proposes semantics naturally coded by this form.