There is a set of Spanish verbs which admit both Indicative and Subjunctive complements. The Indicative complementizer is correlated with a positive presupposition about the truth of the complement; the Subjunctive implies a neutral attitude. This paper shows that these presuppositions must be reflected in the underlying structure of the complement and cannot be explained through the use of surface structure interpretation rules because the presuppositional nature of the subordinate clause affects the application of a number of transformations, even very (...) early ones. Indicative and Subjunctive restrictive relative clauses imply the same types of presuppositions as the Indicative and Subjunctive complements respectively. They can be explained through the same type of configurations which can account for the syntactic and semantic behavior of the two types of complements. (shrink)