The Wh-Feature

A determiner with a wh+ feature is always the left-most determiner in linear order since no determiners have selectional restrictions that allow them to adjoin onto an NP with a +wh feature value. The presence of a wh+ determiner makes the entire NP wh+, and this is correctly represented by the coindexation of the determiner and root NP nodes' values for the wh-feature. Wh+ determiners' selectional restrictions on the NP foot node of their tree only allows them adjoin onto NPs that are wh- or unspecified for the wh-feature. Therefore ungrammatical sequences such as $\ast$which what dog are impossible. The adjunction of wh + determiners onto wh+ pronouns is also prevented by the same mechanism.