Trouble on the left periphery

djuncts may occur (by `adjunct preposingʹ) before a wh-interrogative clause which is a main clause, but not before one which is subordinate; for example: (i) Tomorrow what shall we do? (ii) I told you (*tomorrow) what we shall do. Why should the possibility of adjunct preposing vary between main and subordinate clauses? The pre-theoretical answer is obvious: the wh-word has the extra function in a subordinate clause of signalling the start of a subordinate clause, so like any other subordinator it must be the first element in its clause. Less obvious is how to capture this insight in a formal grammar, and the paper will show that this challenge favours flexible word-based grammars over the more familiar kind which assign a uniform clause structure. The paper considers and rejects a number of examples of the latter approach, especially that of Rizzi [Rizzi, L. 1997. The fine structure of the left periphery. In: Haegeman, L. (Ed.), Elements of Syntax. A Handbook in Generative Grammer. Klewer, Dordrecht, pp. 281–337]. The proposed solution is based on enriched dependency structure (Word Grammar) which makes head-hood ambiguous in certain constructions. In particular, the head of a wh-interrogative may be its finite verb when it is a main clause but must be the wh-element when it is subordinate.