Doubly-filled COMP filter
(i) I wonder who (*that/*whether) she saw
Examples like these have been accounted for by assuming that complementizer deletion must obtain so as to satisfy this filter. The introduction of the CP necessitates an alternative formulation of this filter. The problem of (i) is now the obligatory deletion of COMP in English.
- Riemsdijk, H. van and E. Williams 1986. Introduction to the theory of grammar, MIT Press, Cambridge, Mass.