Syntactic-semantic interrelationships of this kind form the basis of a system of deep structures and rules which account for the complement system of English, and other languages as well. The importance of a system successfully worked out along the general lines suggested above would lie in its ability to account not only for the syntactic structure of sentential complementation, but also for its semantic structure, and for the relationship between the two. Our analysis of presupposition in the complement system contributes a substantial instance of the relation between syntax and semantics, and enables us to correct an error which has been made in most past work on transformational syntax. The error is that different types of complements (that-clauses, gerunds, infinitives) have all been assumed to have the same deep structure, and hence to be semantically equivalent.¹ We have seen that there is good reason to posit a number of different base structures, each mapped by transformations into a syntactic paradigm of semantically equivalent surface structures. The base structures differ semantically along at least two independent dimensions, which express the judgment of the speaker about the content of the complement sentence.

This approach to a theory of complementation is not only more adequate from a semantic point of view. Its purely syntactic advantages are equally significant. It eliminates the need for marking each verb for compatibility with each surface complement type, that is, for treating complementation as basically irregular and unpredicatable. We account for the selection of complement types quite naturally by our proposal that there are several meaningful base structures, whose choice is in large part predictable from the meaning of each predicate. These base structures are subject to various transformations which yield surface structures in which the relation between form and meaning is considerably obscured.

¹ The studies of Lees (i960) and Vendler (1964), however, contain many interesting semantic observations on sentential complementation and nominalization which still await formal description and explanation.