Analysis of the various types of infinitival clauses in Latin, based on the theoretical model of generative grammar. A distinction is drawn between the structure of the Accusative and Infinitive (AcI), and the "control" structures, that is subordinate clauses with a present infinitive verb and a null subject (PRO), which is semantically controlled by an element of the matrix clause. As for the AcI, we formulate the “Null Complementizer Hypothesis”, that is we postulate the existence of an abstract complementizer, which selects an infinitival verb and assigns accusative case to the subject of the inifinitival clause. The null complementizer is only compatible with a typology of the infinitive which is able to morphologically express the whole tense sequence of past, present and future. This hypothesis helps to explain why the AcI does exists in Latin, but not in Italian or English.
