On labeling: Principle C and head movement

In this paper, we critically reexamine the two algorithms that govern phrase structure building according to Chomsky (2008). We replace them with a unique algorithm, the Probing Algorithm, which states that the Probe of any kind of Merge always provides the label. In addition to capturing core cases of phrase structure building, this algorithm sheds light on Principle C effects and on the syntax of wh-constructions, which we analyze as cases of conflict between two Probes. In these two configurations a lexical item (which should become the label, being endowed with an Edge Feature that qualifies it by definition as a Probe) is merged with a syntactic object that, being the probe of the operation, should also become the label. In one case, this conflict produces two alternative outputs (a question or a free relative) that are both acceptable. In Principle C configurations, one of the resulting outputs (the one where the lexical item " wins" ) produces an object that is not interpretable. This way, Principle C effects are reduced to cases of mislabeling, with no need to postulate a specific condition to rule them out. © 2010 The Authors. Journal compilation © 2010 Blackwell Publishing Ltd.