Abstract

Extension embodies an intuition that appears worth preserving, namely, the notion that at any point in a derivation, what counts as the top of the tree at that moment restricts the class of possible operations that can apply. This principle, if a version of it is correct, propels an aggressively derivational view of syntax. However, Chomsky's proposal is too restrictive to permit a wide range of syntactic analyses that appear to be worth preserving, all of which violate Extension by merging constituents near the top of the tree. After some 'fixes' of Extension are rejected, including interarboreal movement, I then propose to revise Extension as Exxtension. The essential idea of Exxtension is to loosen, yet make precise and restrictive, the definition of what counts as (near) the top of the tree. The new definition, to be introduced after some structural assumptions have been established, has interesting consequences for the role of thematic selection and modification once it has been enhanced by the Selection Principle, also to be introduced below. Then all of the analyses discussed that are worth preserving will be shown to be viable within the Exxtension approach, except one, for which a different sort of analysis will be sketched.